Protection varies based on personal risk factors and age
As new Omicron subvariants reshape the pandemic's terrain, federal health officials have offered a measured reassessment of where updated COVID boosters stand: not triumphant, but still standing. CDC data released in late January 2023 confirms that the fall reformulations from Pfizer and Moderna reduce symptomatic infection by roughly half among younger adults, with diminished but real protection for those over 65, and a striking reduction in death risk for those who remain unvaccinated. The findings arrive at a pivotal moment, as regulators prepare to ask whether the nation's relationship with COVID vaccination should settle into the familiar annual rhythm of flu season.
- XBB and XBB.1.5 have displaced the variants the updated boosters were built to fight, accounting for nearly half of all U.S. COVID cases by late January and raising urgent questions about whether the shots can keep pace with the virus.
- Effectiveness sits at a modest 48–52% against symptomatic infection in younger adults and falls further to 37–43% in those 65 and older — a gap that signals real vulnerability in the population most at risk.
- The most striking number cuts through the ambiguity: unvaccinated individuals face a nearly thirteenfold greater risk of COVID death, while those who skipped the updated booster face more than twice the risk of those who received it.
- FDA advisors are convening to weigh whether COVID vaccination should become an annual event, a structural shift that would reframe the entire public health strategy around a virus that keeps rewriting its own rules.
Federal health officials released data on Wednesday showing that the updated COVID-19 boosters introduced last fall are providing meaningful, if imperfect, protection against the variants now driving infections across the United States. The shots, made by Pfizer and Moderna, were originally formulated against the BA.4 and BA.5 Omicron strains — neither of which remains dominant. XBB and its close relative XBB.1.5, descendants of an earlier Omicron branch, now account for nearly half of all U.S. cases, and laboratory studies had raised doubts about how well the existing boosters would hold up against them.
The CDC's real-world analysis, covering cases from December through mid-January, offered a cautiously reassuring answer. Among adults 18 to 49, the updated booster prevented symptomatic infection in roughly half of cases — 52% against BA.5 and 48% against XBB variants. Protection was noticeably weaker in adults 65 and older, where effectiveness fell to 37–43%. Dr. Brendan Jackson, who leads the CDC's COVID-19 response, presented the findings to reporters and stressed that the vaccines continue to work against the strains now circulating.
Separate from the published study, Jackson shared data on severe outcomes that told a more dramatic story. People who had been previously vaccinated but had not received the updated booster faced more than twice the death risk of those who had. For the unvaccinated, the disparity was stark: a nearly thirteenfold greater risk of dying from COVID-19. Researcher Ruth Link-Gelles, who authored the study, noted that these are population-level estimates tied specifically to symptomatic infection, and that individual risk depends on personal health factors.
The release was timed deliberately. On Thursday, outside experts advising the FDA were set to meet and consider whether COVID vaccination should shift to an annual model, much like the flu shot. With XBB.1.5 entrenched as the dominant strain and the virus continuing to evolve, the question of how often — and in what form — Americans should be vaccinated has taken on new urgency. The CDC's immediate message was straightforward: stay current with recommended vaccinations. What that means in the longer term remains an open and consequential question.
On Wednesday, federal health officials released fresh data showing that the updated COVID-19 boosters rolled out last fall are doing what they were designed to do: preventing symptomatic infections from the virus variants now circulating most widely across the country. The news came with an important caveat, though. The protection these shots offer varies significantly depending on age, and it's noticeably lower than what earlier vaccine formulations achieved against previous strains.
The updated boosters, manufactured by Pfizer and Moderna, were originally formulated to target the BA.4 and BA.5 Omicron variants. Those strains are no longer dominant. Instead, XBB and its close relative XBB.1.5 have taken over, accounting for nearly half of all COVID cases in the United States by late January. These newer subvariants descended from an earlier branch of Omicron called BA.2, and laboratory research had raised concerns that the existing boosters might not work as well against them. The CDC's real-world analysis, examining cases from December 1 through mid-January, was meant to answer that question directly.
The findings show the vaccines are holding up reasonably well, though not spectacularly. Among adults aged 18 to 49, the updated booster prevented symptomatic infection in about 52 percent of cases involving BA.5 and 48 percent of cases involving XBB or XBB.1.5. Those numbers represent roughly half of infections prevented—a meaningful but modest level of protection. The picture darkens for older Americans. In people 65 and older, effectiveness dropped to 37 percent against BA.5 and 43 percent against the XBB variants. Dr. Brendan Jackson, who leads the CDC's COVID-19 response, presented the data to reporters, emphasizing that the vaccines are still providing protection against the latest dominant strains.
What the published study did not include, but what Jackson announced separately, was data on severe outcomes. The updated vaccine reduced the risk of death from COVID-19 by more than twofold in people who had previously been vaccinated but had not yet received the updated booster. For the unvaccinated, the protection was far more dramatic: a reduction in death risk of nearly thirteen-fold. Ruth Link-Gelles, the CDC researcher who authored the study, noted that these figures represent population-level benefits. Individual protection varies based on personal risk factors, and the estimates apply specifically to symptomatic infection—cases where people experience at least one symptom of COVID-19.
The timing of this announcement matters. The CDC was releasing the data ahead of a Thursday meeting where outside experts advising the Food and Drug Administration were expected to discuss whether the United States should transition to offering COVID vaccines as an annual shot, similar to the influenza vaccine. The question of how often Americans should be vaccinated against COVID-19 has become increasingly urgent as the virus continues to evolve and new variants emerge. With XBB.1.5 dominating the landscape, the CDC's message was clear: people should stay current with their recommended COVID-19 vaccinations. Whether that means annual shots, boosters on some other schedule, or a different approach entirely remains to be decided.
Citas Notables
Today we have additional evidence to show that these updated vaccines are protecting people against the latest COVID-19 variants— Dr. Brendan Jackson, CDC COVID-19 response director
The vaccines cut the risk of symptomatic infection by about half on a population level, but individuals see different benefits based on their risk factors— Ruth Link-Gelles, CDC study author
La Conversación del Hearth Otra perspectiva de la historia
So the updated booster works about half the time against the dominant variant. That sounds like it's not very good.
It depends on what you're measuring. Half of symptomatic infections prevented is meaningful—it's the difference between getting sick and not. But you're right that it's lower than what we saw with earlier variants. The real story is what happens to severe disease and death, which dropped much more dramatically.
Why is the protection so much lower in older people? Is the vaccine itself less effective, or is something else happening?
The study doesn't fully explain the mechanism, but older adults generally have weaker immune responses to vaccines. Their bodies don't mount as robust a defense. That's why the gap between 48 percent protection in younger adults and 43 percent in older adults might actually reflect both the vaccine's performance and the aging immune system itself.
The booster was designed for BA.4 and BA.5, but now XBB is dominant. Does that mean the vaccine is outdated?
Not exactly. The fact that it still works at 48 percent against a variant it wasn't specifically designed for suggests the immune response is broader than just targeting one strain. But yes, there's a mismatch. That's probably why the FDA is meeting tomorrow to discuss whether we need to update the formula again or shift to annual shots.
What does a thirteen-fold reduction in death risk actually mean for an unvaccinated person?
It means if you're unvaccinated and get infected, you're roughly thirteen times more likely to die than if you'd been vaccinated. That's a massive difference. It's why the CDC is emphasizing vaccination even when symptomatic infection rates are moderate.
So people should get the booster even though it only prevents infection about half the time?
Yes. Because preventing infection is one benefit, but preventing death is another—and that protection is much stronger. Plus, preventing even half of symptomatic cases means fewer people getting sick, spreading the virus, or developing long COVID. It's not perfect, but it's substantial.