March 14, 2025 – Vaccines grab a lot of headlines these days, but three significant updates may have escaped your radar. Here’s why they matter.
Norovirus: Scientists May Finally Be on to a Vaccine
Respiratory viruses are getting all the attention, but the stomach bug – norovirus, formally – has also made a big impact this winter.
More than 100 outbreaks have been reported weekly since Christmas, which is two to three times the usual number.
Besides trying to stay hydrated, not much can be done for the GI tract infection that causes sudden and severe vomiting and diarrhea, and infects more than 700 million people worldwide each year.
It’s also a difficult virus to target with a vaccine, although scientists are trying.
Last week, researchers reported two big leaps forward in that quest: promising results toward an oral vaccine in one study, and strong leads on how to target multiple genotypes in another.
Genotypes are like strains, and targeting multiple ones will likely be key.
"Human noroviruses are very diverse – much more so than even SARS-CoV-2," the virus that causes COVID-19, said norovirus expert Craig Wilen, MD, PhD, an associate professor of laboratory medicine and immunobiology at Yale University in Connecticut. (He was not involved in the new studies.)
Developing a vaccine "that can protect against all human norovirus genotypes" has been a challenge, he said.
The latest discoveries also could inform development of a treatment for norovirus-associated gastroenteritis, according to a news release from the University of Texas at Austin, where first author Juyeon Park, PhD, is a postdoctoral researcher.
In the other new paper, researchers at San Francisco-based Vaxart reported that a norovirus vaccine tablet taken by older people could elicit antibodies that were found not only in the blood of people in the study, but also in the saliva and the mucous lining of the nose. A previous study had already established a similar response in the intestine.
The vaccine activated T and B cells – pathogen-fighting immune cells – which "showed they had the capacity to migrate to mucosal tissues," said study author Becca Flitter, PhD, MPH, the director of immunology at Vaxart.
"While the intestine might be a key site of infection for norovirus, we can’t rule out the possibility that other tissues can also be infected," she said. "So creating a broader response might be important."
Another strength: "It’s given as an oral tablet and appears to induce an immune response in the gut where norovirus replicates," Wilen said. "This likely has advantages over systemic vaccines, which may have less activity in the gut."
Several other norovirus vaccine candidates are in the works, including one from Boston-based Hillevax and another from Moderna (now on hold pending an investigation of a reported case of Guillain-Barre syndrome, a rare neurological disorder).
Still, a norovirus vaccine remains at least a couple of years away, Wilen said.
"The greatest impact of a human norovirus vaccine," he said, "will be children under the age of 5 in low- and middle-income countries. This is where the disease burden and mortality are greatest."
COVID: This Season’s Vaccine ‘Not a Slam Dunk’ But Helpful
New CDC data shows that midseason, the latest version of the COVID-19 vaccine has been 33% effective against adult emergency room or urgent care visits due to COVID. That’s compared to an estimated effectiveness of around 25% last season.
The number may have been impacted by the unusually strong presence of COVID this past summer, researchers said. The summer surge may have boosted immunity, giving many people some protection and making the new vaccine seem less effective than it really is.
The vaccine effectiveness "should therefore be interpreted as the added benefit of 2024-2025 COVID-19 vaccination," the CDC report said.
Among people ages 65 and older who don’t have impaired immune systems, this season’s vaccine was 45% effective against hospitalization due to COVID. Vaccine effectiveness among older adults who are immunocompromised was 40%. The data covers the period from September to January, and effectiveness was measured for the period of one week to four months after getting vaccinated.
Another thing that may be affecting the data is that the virus has mutated to be more contagious and less deadly, said Charles Semelka, MD, MS, a doctor who specializes in aging biology and frailty at Wake Forest Baptist Health in Winston-Salem, North Carolina, and who has studied COVID vaccine response.
For people who think the effectiveness data sounds low and therefore potentially make the shot less worthwhile, Semelka said: "It’s not a slam dunk, but it’s helpful, especially for people with chronic health conditions. This could mean a milder course and increased protection from severe complication."
The CDC researchers wrote that they couldn't estimate vaccine effectiveness among children because of the combination of low vaccination and hospitalization rates among those ages 5 to 17.
This season, 23% of adults reported getting the latest COVID shot, including 45% of people ages 65 and older. COVID vaccine uptake is lagging far behind that of flu shots this season, with 45% of adults saying they got a flu shot, including 70% of older adults. Although relatively new, 47% of adults age 75 and older said they got an RSV vaccine.
HPV: Vaccine Lowers Cervical Cancer Risk in First Real-World Cohort
The first group of girls to receive the human papillomavirus (HPV) vaccine are now in their early to mid-20s, and early data shows that young women of this generation are 80% less likely to be diagnosed with precancerous lesions of the cervix.
The results point toward a potentially dramatic future impact on rates of this highly preventable cancer.
"These findings reinforce the importance of routine childhood vaccination against HPV infection," said CDC spokesperson Paul Prince.
The new CDC report analyzed rates of precancerous lesions among women ages 20 to 24 from 2008 to 2022.
The CDC recommends that all girls and boys get the HPV vaccine, which is marketed under the brand name Gardasil 9. Ideally, kids should get the shots at 11 or 12 years old, the CDC says, but the American Academy of Pediatrics suggests considering it as early as 9 years old.
The vaccination schedule is recommended because it works well – preteens produce more antibodies after an HPV vaccination than older teens do. The vaccine protects against 90% of cancers caused by the virus, including all cases of cervical cancer as well as nearly 100% of cases of genital warts. HPV is so common that nearly all people get at least one type of HPV during their lifetime.
The most recent available estimate shows that about 39% of children ages 9 to 17 years old had received one or more doses of the HPV vaccine as of 2022. Children with private health insurance or Medicaid coverage were the most likely to get vaccinated, and children with no insurance were significantly less likely.
