For the millions of people who have taken up the sport of rock climbing, a cliff face is a challenge, a vertical puzzle solved only with the proper placement of hands and feet. Look closely, though, and those crevices and cracks that provide hand- and footholds also provide homes for a variety of plants, invertebrates and other easily overlooked species.

People who participate in outdoor sports like rock climbing may not think about the environmental impact of what they’re doing. After all, how big of an impact can one person really have on a rock? But there is a potential for harm, notes ecologist Andrea Holzschuh of the University of Würzburg in Germany. Finding evidence of that harm, though, is a challenge — the features that make some cliffs fun to climb, or not, also make for complicated research.

Holzschuh became interested in the effects that climbers are having on the environment in part because she is a climber herself, partial to tackling rocks in the Frankenjura region of Germany, which is noted for having some of the best climbing in Europe. The plants, animals and other species that make the cliffs their home, she notes, are often specialists that have found ways to adapt and even thrive in the extreme conditions found on the rock face. They may be rare or completely absent from nearby spots, and they often are slow-growing and their numbers grow only in spurts.

And then come the climbers, who may trample what grows at the bottom of a cliff, dig out whatever is growing in a crevice to gain a better handhold, spread species not native to the area or taint the rock face with chalk, altering pH or nutrient conditions for whatever is growing there. Rock climbing isn’t quite as impact-free as some might assume.

But scientists haven’t really been able to adequately assess that impact. Holzschuh went looking for research on this topic and found only 22 studies that tested how rock climbing might affect plants or animals. She tossed out six of those studies because they failed to make comparisons with unclimbed areas or had other major design problems that made it impossible to tease out effects. The remaining 16 studies found a variety of impacts on organisms ranging from lichens to snails to cedar trees. Holzschuh’s review appears in the December Biological Conservation.

But what the review really highlights is just how difficult it is to study rock climbing’s potential impacts. Holzschuh says a big challenge is in finding appropriate unclimbed cliff faces to compare to those that rock climbers frequent — ones that share traits such as slope and how much sunlight the face gets. “Often, all cliffs in a regions that are attractive for climbers are climbed and only cliffs that do not resemble the climbed cliffs in all abiotic traits remain unclimbed,” she notes. “Then no reliable study can be conducted.”

And then, of course, there’s the inaccessibility of many cliffs and the difficulty in studying even the accessible ones. “How many people have these skills and the flexibility to work on these projects?” says Michael Tessler of the American Museum of Natural History and Fordham University. Plus, he notes that a subset of rock climbing called bouldering — in which climbers tackle boulders or short cliff faces measuring less than 3.5 meters high, without using safety ropes — is especially popular with younger people. “Professors inherently aren’t always young,” he notes.
Tessler and colleague Theresa Clark of the University of Nevada, Las Vegas published the first ever analysis attempting to quantify the impact of bouldering on the environment. This type of climbing has similar potential for ecosystem damage as roped rock climbing, they note, plus a couple of additional ones: Boulderers often clear the ground below of rocks and logs so that they can place crash pads in case of falls, and they may be more likely to trample anything at the top of a boulder or cliff, rather than coming directly down.

Tessler and Clark tried to measure the impact of climbers at bouldering routes in the Shawangunk Ridge, a popular climbing site in New York where Tessler climbs. They compared transects in climbed boulder routes with transects along nearby unclimbed sections of rock and found differences in lichen, moss and woody plants. None of this added up to a major threat, but conservation managers might want to monitor these activities in remote sites and shut down certain routes that are proving too popular — and potentially too harmful to whatever is growing there, Tessler and Clark suggest in the December Biological Conservation.

While we still can’t really say how much impact climbers might be having on the rocky environments they climb, there is a definite need for more scientists to strap on their climbing shoes and tackle the questions of climbing’s impact. (Try it! It’s lots of fun!) But climbers, too, can do their part, Holzschuh and Tessler say.

“I think climbers can easily minimize their impact on the cliff vegetation if they do not willingly remove vegetation from the cliff to ‘clean’ hand- and footholds in the climbing route. Climbers should not access the cliff plateau [and should] leave this cliff part completely undisturbed,” Holzschuh says. “At the cliff base, bags and gear should be laid down within a small area to reduce the effects of trampling.”

Tessler also has advice. “Boulderers should be aware that even infrequent climbing leaves some impression on rock-associated vegetation,” he says. “They should remove as little vegetation and soil when climbing and establishing climbs. Also, if a climb is wet, dirty or covered in vegetation, maybe go to another one. This is an easy way to ensure that some rock faces can stay more natural.”

And if climbing is restricted because, say, rare birds are breeding there, rock climbers should obey the restriction and go climb somewhere else, Holzschuh says. There are plenty of other cliffs to be conquered.

A team of scientists may have given hydrogen a squeeze strong enough to turn it into a metal. But critics vigorously dispute the claim.

Researchers from Harvard University report that under extremely high pressures hydrogen became reflective — one of the key properties of a metal. The feat required compressing hydrogen to 4.9 million times atmospheric pressure, the scientists report online January 26 in Science.

If correct, the result would be the culmination of a decades-long search for a material that could have unusual properties such as superconductivity — the ability to conduct electricity without resistance.
But physicist Eugene Gregoryanz of the University of Edinburgh, who works on similar experiments, decries the study’s publication as a failure of the journal’s review process. Given the evidence presented in the paper, Gregoryanz is skeptical that the claimed pressures were actually reached and notes that the researchers presented results from only one experiment. “How is it possible to do only one experiment and claim such a big thing?” he says.

Physicist Alexander Goncharov of the Carnegie Institution for Science in Washington, D.C., also takes issue with the researchers’ conclusions. “It’s not shown whether they have hydrogen at all at high pressure,” Goncharov says.

Not everyone is so skeptical. “I think there’s a good chance that it’s correct,” says theoretical physicist David Ceperley of the University of Illinois at Urbana-Champaign. The pressure at which the hydrogen became reflective is about where theoretical physicists have calculated that a metal should form, Ceperley says.

Theorists’ calculations also indicate that metallic hydrogen could be a high-temperature superconductor (SN: 8/20/16, p. 18). Most superconductors work only in extreme cold, but metallic hydrogen might function even at room temperature — higher than any other known superconductor. If so, its discovery would raise hopes that superconducting metallic hydrogen could be used in power lines, making transmission of electricity vastly more efficient.

To put the pressure on hydrogen, scientists capture it as a gas between the tips of two diamonds and squeeze them together. It’s no easy task. “The problem in making metallic hydrogen has been that the predicted pressures have been very high,” says physicist Isaac Silvera of Harvard University, a coauthor of the study. “Diamonds always break before you can obtain those pressures.”
To stave off breakage, the scientists smoothed the surface of the diamonds to remove any defects and covered the gems in a thin layer of aluminum oxide to prevent hydrogen from diffusing inside and creating cracks. The researchers also cooled the setup to temperatures of 83 kelvins (−190° Celsius) or below. As the scientists ratcheted up the pressure, the hydrogen first turned black, indicating a possible semiconducting phase, then became reflective, indicating a metal. The metallic hydrogen could be either a solid or a liquid, Silvera says.

But such experiments are tricky — only a few teams of researchers in the world are capable of performing them. One of the pitfalls can be that the hydrogen escapes from the chamber without the scientists realizing it. However, Silvera says, “We’re sure we have hydrogen in there.”

Some previous metallic hydrogen experiments have monitored hydrogen as the pressure is ramped up to help ensure that the hydrogen hasn’t escaped and to study its evolution. To do so, scientists use a technique called Raman spectroscopy, which involves shining a laser through the diamonds and observing the scattered light. But at pressures this high, lasers could cause the diamonds to break, Silvera says. So the researchers used lasers only after the sample had reached the metallic state.

Silvera’s group is not the first to announce the discovery of metallic hydrogen. Earlier claims of finding the metal have been overturned (SN: 12/17/11, p. 9). “It’s not the last word,” says Ceperley. “It should encourage all the other groups to come out and try to reproduce it.”

A roughly 540-million-year-old creature that may have once skimmed shorelines was a real oddball.

Dozens of peculiar, roundish fossils discovered in what is now South China represent the earliest known deuterostomes, a gigantic category of creatures that includes everything from humans to sea cucumbers.

No bigger than a pinhead, the fossils have wrinkly, baglike bodies and gaping mouths that are pleated around the edges like an accordion, researchers report January 30 in Nature. Unlike most other deuterostomes, the animals don’t seem to have an anus. Instead, the ancient oddities, named Saccorhytus coronarius, may have leaked waste (and other bodily fluids like mucus and sex cells) out of tiny holes lining their sides. These holes may have later evolved into gill slits.

A tough, flexible skin would have protected Saccorhytus as it wriggled through grains of dirt, the authors suggest. The find supports previous suggestions that the earliest deuterostomes were actually a kind of water-dwelling worm.

Are you feeling the pressure of Valentine’s Day and in need of advice on how to find someone special? The animal world has some advice for you.

Make sure you look nice.
There’s no need to go for an entire makeover, but looking your best is usually a good idea when on the search for a partner. Male black-and-white snub-nosed monkeys appear to have taken a lesson from Revlon — they go for the rouge-lipped look during the mating season. Those with bright, red lips tend to be surrounded by females.
Learn to dance …
As anyone who has ever watched John Travolta in Saturday Night Fever knows, having the right dance moves can make finding a mate easier. For some animals, it’s essential. That’s true for male peacock spiders, which raise colorful flaps on their behinds and wave them while lifting their third legs in an adorable dance aimed at luring a mate. And if a guy doesn’t have the best moves or try hard enough, females don’t just reject him — they get aggressive.

… and how to flirt.
Even if you’re an expert dancer, you’ll probably need to do at least a little flirting. It may be a bit more subtle than torrent frogs, though, who turn flirting into a big production. A male frog will get a female’s attention by first calling out and puffing up his vocal sacs. Then he’ll shake his hands and feet and wiggle his toes. If he’s successful, the female will let him know with a special call.

Attend a party.
The best place to put all of this on display is, of course, a party! And there are parties everywhere, even at the bottom of the ocean. Scientists exploring a seamount off the Pacific coast of Panama in 2015 found an enormous party of small, red crabs swarming all over each other. Such large aggregations are common among crab species and may be linked to reproduction.

Practice, practice, practice.
Once you’ve landed a partner, you might want to serenade him or her with the perfect love song. But first you’ll need to practice, just like great reed warblers (probably) do. Males spend their entire winter vacation singing the songs they seem to use to woo the ladies come spring. All that singing cuts into time the guys could spend foraging for food or resting, but that practice might pay off because female warblers prefer males that sing more complex tunes.

Keep an eye on the competition.
You may not be the only one interested in your partner, so make like a peacock and check out your competition. Peacocks fan out their feathers to lure the ladies, but females only pay attention to what’s happening at the bottom of the show, studies have revealed. Males do likewise, keeping their gaze tuned to the bottom of the competition’s display.

Bring a gift.
You probably don’t need to worry that your partner will go cannibal, but that doesn’t mean you can’t take a hint from a species where that does happen. When approaching a female, male nursery spiders are smart to bring a gift of a big dead insect wrapped up in silk. The gift will not only keep the female busy while the male mates with her, but it can also double as a shield if she sees him as a potential meal rather than a mate.

Saved by the Bell
Physicists used light from stars to perform a cosmic Bell test, which verified that quantum particles were indeed “spooky,” Emily Conover reported in “Quantum effect passes space test” (SN: 1/21/17, p. 12).

Reader George Mitchell took issue with Conover’s description of entangled photons before they are measured as having multiple polarizations at once. “We don’t know the direction of their polarization,” Mitchell wrote. “It is undefined.”

“Multiple polarizations” in this context is meant to indicate that there are multiple possible outcomes of a polarization measurement; the particle does not have a definite polarization that is simply unknown. “Bell tests like the one in the a­rticle confirm this interpretation,” Conover says (SN Online: 1/27/16).
It’s similar to how Schrödinger’s cat can be in a “superposition” of both alive and dead at the same time (SN: 11/20/10, p. 15). “It’s not that we don’t know whether the cat is alive or dead; it’s both,” she says. “This is hard to wrap one’s head around.” In any case, it is effectively impossible to put a real cat in a superposition, because it is too large to display the strange properties of quantum mechanics. “But for particles,” she says, “this is acceptable behavior.”

Land ho
From Nuna to Pangaea, shifting landmasses have repeatedly reshaped Earth’s surface. Researchers are now picturing a future s­upercontinent dubbed Amasia, due in 250 million years, Alexandra Witze reported in “Supercontinent superpuzzle” (SN: 1/21/17, p. 18).

Reader Pierre Grillet wondered how subduction — the process by which a tectonic plate is pushed beneath another tectonic plate — could pull continents apart. “I would suggest that a different mechanism is also at work here. Rising material must balance crust material being subducted into the mantle,” he wrote. “It would make sense that this rise should occur in the center of the plate, where the mantle is hotter. Rising material would then spread sideways, pushing the sides of the plate over the oceanic crust and pulling the plate apart.”

The process Grillet describes is a theory proposed by some researchers. Other researchers have doubts (SN: 4/4/15, p. 13). “Plumes of hot material rising from the mantle could rip continents apart, but the plumes would have to rise up at weak points along continental boundaries, which seems unlikely,” says Thomas Sumner, Science News’ earth sciences writer. A competing theory covered in the story suggests that subduction tears continental plates apart by pulling at their edges.
Power up
A variety of next-generation batteries promise to store energy more efficiently, providing power for longer periods, Susan Gaidos reported in “Charging the future” (SN: 1/21/17, p. 22).

Reader Tom Wicker was disappointed that the beginning of the story equated power and energy. “Everybody wants more power from their batteries,” Gaidos wrote, citing smartphone, laptop and electric-car batteries as examples.

“Laptop batteries can supply more than enough power. You need to charge them frequently because of the limited amount of energy they store,” Wicker wrote. “It is of course correct that drawing more power, more energy per unit time, from a battery will drain it faster. But that is true even though the battery may have no problem supplying the required amount of power. It just can’t do that for as long as required due to insufficient energy storage.”

Wicker’s distinction between energy and power is correct, Gaidos says. “When talking about batteries, the term ‘portable power’ is frequently used, when what is really meant is portable energy. The research under way, as described in the story, aims to create batteries with high power that can maintain that power through a large number of recharge cycles,” she says.

Three high-energy neutrinos have been spotted traveling in tandem.

The IceCube Neutrino Observatory in Antarctica detected the trio of lilliputian particles on February 17, 2016. This is the first time the experiment has seen a triplet of neutrinos that all seemed to come from the same place in the sky and within 100 seconds of one another. Researchers report the find February 20 on arXiv.org.

Physicists still don’t know where high-energy neutrinos are born. The three neutrinos’ proximity in time and space suggests the particles came from the same source, such as a flaring galaxy or an exploding star. But the scientists couldn’t rule out the possibility of a fluke — the triplet could simply have been the result of accidental alignment between unassociated neutrinos.

Eight different telescopes followed up on the neutrino triplet, checking for some sign of the particles’ origins. The telescopes, which searched for gamma rays, X-rays and other wavelengths of light, found nothing clearly associated with the particles. But scientists were able to rule out some possible explanations, like a nearby stellar explosion caused by the collapse of a dying star.

Here’s one good reason why people often take medications and use health products that don’t live up to expectations or just don’t work — digital word of mouth.

The reviews can be glowing. Take this scuttlebutt about a cholesterol treatment: “I have been using this product for 2 years. Within the first 3 – 4 months my cholesterol was down 30 points. Just got cholesterol tested last week: down from 245 to 196.”

That’s incredible. It might even be true. But the big picture is alarming: Patients’ online reviews of three over-the-counter drugs — two for lowering cholesterol and one for losing weight — greatly exaggerate how well these substances actually work for most people, says psychologist Mícheál de Barra of the University of Aberdeen in Scotland. Online reviewers portray these medications as working three to six times better than they do in clinical trials that randomly assign drugs or placebos to broad samples of volunteers, he says.

“To learn what works in medicine, you need systematically collected data, usually randomized clinical trials,” de Barra says. “It’s very risky to rely on observations and word of mouth, whether it’s electronic or in person.”

Online reviewers probably aren’t lying, at least not in most cases. Neither are online review readers unrealistically optimistic about health treatments. The problem is that people who benefit most from a medication are especially apt to post their experiences online. Review readers get bamboozled by a wave of positive recommendations that don’t accurately represent how a drug works, or doesn’t work, for people in general.

The duping doesn’t end there. Direct word of mouth about medical treatments, as well as glowing testimonials about health products in advertisements, also traffic in positively skewed information.

In some cases, science does, too. Researchers have recently raised alarms about the “file-drawer problem,” in which studies that find no statistical effects are not published (SN: 5/19/12, p. 26). Published studies reporting positive effects then look unjustifiably bulletproof.

Clinical trials can tilt results in other ways as well. Authors of published trials often fail to preregister details of what they plan to study and how they’ll measure it, enabling data manipulation, selective reporting of results and self-serving interpretations of findings. Clinical trials report patients’ “average” responses to, say, an anticholesterol drug, but do a poor job of predicting which individuals will benefit from that treatment. “Published evidence from randomized trials is already an amalgam of evidence-based medicine and hearsay,” notes Stanford University epidemiologist John Ioannidis.
Online reviews are just old-fashioned word of mouth with a global bullhorn. But they offer one way to quantify the positive bias inherent in so much communication about medical treatments. Patients’ medication reviews that include numerical information, such as cholesterol levels before and after taking an anticholesterol drug, represent what Ioannidis calls “evidence-based hearsay.” Even if patients’ reviews rate treatments with a star system rather than including quantified measures of some kind, those opinions become powerful hearsay evidence for other patients, Ioannidis suspects.

De Barra evaluated 908 online reviews of two cholesterol reduction products, Benecol caramel smart chews and CholestOff, written on or before March 18, 2015. He also assessed 767 reviews of a weight-loss drug, Alli (orlistat), written on or before February 28, 2015.

Benecol reviewers reported a not-too-shabby average cholesterol decline of 45 milligrams per deciliter, versus a small average decline of 14 milligrams per deciliter in nine clinical trials. Respective numbers for CholestOff were 31 milligrams per deciliter and 13 milligrams per deciliter. Alli reviewers reported an average weight loss of about 10 kilograms after taking the drug for three months, versus an average of about two or three kilograms in two clinical trials. That disparity widened slightly after taking Alli for seven months.

Each drug garnered mainly positive reviews, some reporting effects far larger than the average, peppered with a few pans, De Barra reports in the March Social Science & Medicine.

What’s particularly concerning is that these three medications displayed small or negligible effects in clinical trials that probably already inflated how well the drugs work, Ioannidis says. So people searching for help in lowering cholesterol or shedding pounds may instead be getting a massive dose of disappointment from online reviews.

Online reviews can also exaggerate a treatment’s worst effects, whether real or alleged. Evidence-based hearsay may be particularly catchy online and in person when it’s frightening, de Barra suspects.

The anti-vaccination movement provides a potent example, due in part to the success of vaccines. When people face no immediate threat from measles or other infectious diseases, anti-vaccine stories may go viral, so to speak, thanks to misapplied but deeply felt intuitions. Two cognitive scientists, Helena Miton of Central European University in Budapest and Hugo Mercier of the Cognitive Sciences Institute in Bron, France, proposed this scenario in the November 2015 Trends in Cognitive Sciences.

However medical treatments acquire halos or horns, only well-conducted, transparent clinical trials can identify effective medical treatments, such as childhood vaccinations, and their potential side effects, Ioannidis says. But an ominous research trend is gathering steam, he warns. Researchers, professional societies, funders and lobbyists increasingly push to replace clinical trials of randomly selected volunteers with studies of interventions for select samples of people who eat certain foods, take certain drugs or behave in certain ways. The latter investigations may inflate a treatment’s effects even more than online patient reviews do, Ioannidis asserts.

Perhaps a new wave of studies showing how evidence-based hearsay misrepresents many medications will be just what the doctor ordered to resuscitate evidence-based medicine, he muses.

Remnants of a royal palace in southern Mexico, dating to between around 2,300 and 2,100 years ago, come from what must have been one of the Americas’ earliest large, centralized governments, researchers say.

Excavations completed in 2014 at El Palenque uncovered a palace with separate areas where a ruler conducted affairs of state and lived with his family, say archaeologists Elsa Redmond and Charles Spencer, both of the American Museum of Natural History in New York City. Only a ruler of a bureaucratic state could have directed construction of this all-purpose seat of power, the investigators conclude the week of March 27 in Proceedings of the National Academy of Sciences.

The royal palace, the oldest such structure in the Valley of Oaxaca, covered as many as 2,790 square meters, roughly half the floor area of the White House. A central staircase connected to an inner courtyard that probably served as a place for the ruler and his advisors to reach decisions, hold feasts and — based on human skull fragments found there — perform ritual sacrifices, the scientists suggest. A system of paved surfaces, drains and other features for collecting rainwater runs throughout the palace, a sign that the entire royal structure was built according to a design, the researchers say.

El Palenque’s palace contains no tombs. Its ancient ruler was probably buried off-site, at a ritually significant location, Redmond and Spencer say.

A new species of worm-snail is rather snotty. Thylacodes vandyensis shoots out strands of mucus that tangle together, building a spiderweb-like trap for plankton and other floating snacks, researchers report April 5 in PeerJ.

Other worm-snails use this hunting technique, but T. vandyensis stands out because of the “copious amounts of mucus” it ejects, says coauthor Rüdiger Bieler. This goo net, which can stretch up to 5 centimeters across, exits the animal’s tentacles at, of course, “a snail’s pace,” jokes Bieler, a curator at the Field Museum of Natural History in Chicago.

Like other worm-snails, T. vandyensis permanently glue themselves to spots. Bieler found T. vandyensis, which typically grow half as tall as a pinkie finger, on the hull of a sunken ship in the Florida Keys. But they don’t belong there: DNA analysis shows that this invasive species’ closest relatives are in the Pacific Ocean. The worm-snail may have made its way to the Atlantic as a stowaway on a ship.

Cancer prevention isn’t the first thing that comes to many parents’ minds when they consider vaccinating their preteens against human papillomavirus, or HPV. And the fact that HPV is transmitted sexually gives the vaccine more baggage than a crowded international flight. But what gets lost in the din is the goal of vaccination, to protect adolescents from infection with HPV types that are responsible for numerous cancers.

Newly released estimates show just how prevalent HPV infections are in the United States. In April, the U.S. Centers for Disease Control and Prevention reported for 2013-2014 that among adults ages 18 to 59, 25 percent of men and 20 percent of women had genital infections with HPV types that put them at risk of developing cancer.

That’s just a snapshot in time. For those who are sexually active, more than 90 percent of men and 80 percent of women can expect to become infected with at least one type of HPV during their lives. About half of those infections will be with a high-risk HPV type.

“People who think, ‘I’m not at risk,’ are really not understanding the magnitude of this virus,” says cancer epidemiologist Electra Paskett of Ohio State University in Columbus.

HPV is the most common sexually transmitted infection in the United States. The HPV group of viruses includes low-risk and high-risk types. Low-risk types 6 and 11 are responsible for 90 percent of all genital warts. The high-risk types of HPV can cause cancer, and the two behind most HPV-related cancers are types 16 and 18. Seventy percent of cervical cancers can be traced back to types 16 and 18, while type 16 also causes cancers of the anus, vagina, penis and the oropharynx, the part of the throat at the back of the mouth. HPV spreads by sexual contact, either vaginal, anal or oral.
Nationally, from 2011 to 2014, 11 percent of men ages 18 to 69 had an oral infection with any type of HPV, and for nearly 7 percent of men, it was a high-risk type, the CDC’s National Center for Health Statistics estimated in its April report. For women in this age group, it was 3 percent and 1 percent, respectively.

The numbers are far worse when it comes to genital HPV infections. During 2013 to 2014, 45 percent of men and 40 percent of women ages 18 to 59 had genital infections with any type of HPV. One in four men and one in five women in this age group were infected with a high-risk type.

“It’s a wake-up call for both genders, but particularly for males,” says Jessica Keim-Malpass, a nurse scientist at the University of Virginia in Charlottesville.

For an estimated 19,200 women and 11,600 men each year, HPV infections result in a cancer diagnosis.

Vaccination could greatly relieve this cancer burden. Three different HPV vaccines have been available in the United States. The first, introduced in 2006, covered low-risk types 6 and 11 and high-risk types 16 and 18. The most recent HPV vaccine protects against these four types as well as five more high-risk types, and is the only vaccine currently distributed nationally. A federal advisory committee recommended routine vaccination against HPV at 11 or 12 years of age in 2006 for girls and in 2011 for boys.

But the HPV-cancer prevention message doesn’t seem to be getting through in the United States. HPV vaccination rates lag behind the national coverage goal of 80 percent for 13- to 15-year-olds. In 2015, among U.S. adolescents ages 13 to 17, six out of 10 girls and five out of 10 boys had gotten at least one shot in a three-shot series. But only four out of 10 girls and three out of 10 boys had completed the series.

What’s with the lackluster response?

Parents are part of the issue. “They don’t know about the vaccine, or they have fears about safety, or they say ‘My child is not going to be at risk for HPV infections,’” Paskett says.

The safety of all three vaccines was established in large clinical trials before approval by the U.S. Food and Drug Administration. Since 2006, almost 90 million doses of HPV vaccines have been administered nationally, and the most common side effects are soreness or swelling at the site of the shot.

Some parents think that “by giving the vaccine, you are saying it’s OK to have sex,” notes Keim-Malpass. Research doesn’t back this up. A 2012 study in Pediatrics of 11- to 12-year-old girls found that HPV vaccination was not tied to increased sexual activity, as measured by medical records of sexually-transmitted infection or pregnancy. A 2015 study in JAMA Internal Medicine of 12- to 18-year-old girls found no evidence to link HPV vaccination with higher rates of sexually transmitted infections.

The recommended age for vaccination ensures that preteens are protected before they are exposed to HPV, whenever that may be. “The whole reason the vaccine is targeted to 11- and 12-year-olds is to get kids vaccinated before they enter a sexual relationship,” says Keim-Malpass.

Lack of urgency is a problem, too. The delay between an infection and a future cancer can make people complacent about HPV. “You are protecting yourself from an infection, but it has ramifications years, decades later,” Keim-Malpass says. “It’s not about something you get tomorrow, it’s about something you could get 20 to 30 years from now.”

Another difficulty has been the vaccination schedule. The initial recommendation was for three doses, with the second shot one to two months after the first, and the third shot six months after the first. This schedule was challenging for busy adolescents, notes Keim-Malpass.

Now there is a new dosing regimen. For adolescents who begin vaccination before turning 15, only two shots are required, with the second one coming six to 12 months after the first. This should be easier to accommodate in yearly well-child visits.

Even with the suboptimal vaccination rates, there has been an impact on infections. A 2016 Pediatrics study found that, within six years of the first vaccine’s introduction in 2006, infections with the four HPV types covered decreased 64 percent among 14- to 19-year-old girls. There are also fewer cases of genital warts among U.S. teens since 2006.

Any decline in infection rates is a good thing. But “it’s not to the extent we could have, if from the get- go, people realized this was a cancer vaccine,” says Paskett. “If there was a vaccine for breast cancer, moms would be lining up around the corner with their daughters.”