- COVID-19 vaccines remain effective against severe disease, hospitalization, and death.
- For people with weakened immune systems, getting a booster dose after three primary doses is recommended.
- There’s not enough evidence to suggest non-immunocompromised individuals need a second booster shot at this time.
Research shows that a booster or third dose of an mRNA COVID-19 vaccine provides greater protection against infection from Omicron. However, some evidence suggests that booster protection wanes by about 15% to 25% after 10 weeks. Does this mean we’ll need a fourth vaccine dose sometime soon?
Currently, there’s not enough evidence to support the need for a second booster shot among non-immunocompromised individuals. The Centers for Disease Control and Prevention (CDC) only recommends that people with weakened immune systems get a booster shot on top of their three primary doses.
However, that could change soon.
How Long Are Boosters Effective For?
On Friday, Feb. 11, 2022, the CDC published a study showing that both Pfizer and Moderna’s booster shots lost substantial effectiveness after four months during the Omicron surge.
Researchers found that boosters were highly effective against severe and moderate illness for about two months after an initial vaccine series. But once the fourth-month mark hit, that effectiveness significantly declined. The study said this suggests the need for additional boosters in the future.
During those first two months post-booster, the vaccine was 91% effective at preventing hospitalization. But after four months, that dropped to 78%.
Vaccines were also less effective at preventing emergency department and urgent care visits during the Omicron period. Booster protection went from 87% in the first two months to 66% after four months. After five months that number fell to 31%. However, researchers say that the latter number is "imprecise" because there was little data on people who’d received a booster five months prior.
These findings come with caveats. Researchers did not evaluate whether there were differences in protection by age, underlying health conditions, or whether someone was immunocompromised.
"We are still learning about the duration of protection conferred by booster doses against Omicron," William Moss, MD, executive director of the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health, told Verywell. "COVID-19 vaccine effectiveness against the Omicron variant depends on the type of vaccine, the outcome of interest, the number of doses received, the vulnerability of the vaccine recipient, and the time since vaccination."
But we do know that boosters provide significant protection.
"In fact, analyses have shown that for people who are up to date in their vaccinations—which includes two Pfizer and Moderna shots plus one booster or one J&J shot plus one booster—rates of hospitalization and death were very low during the Omicron wave compared to people who were unvaccinated," Leslie M. Kantor, PhD, MPH, professor and chair of the Department of Urban-Global Public Health at the Rutgers School of Public Health, told Verywell.
In December 2021, rates of COVID-19-associated hospitalizations were 45 times higher among unvaccinated people aged 50–64 and 51 times higher in people aged 65 and older, compared to fully vaccinated individuals who got their booster or additional dose, she added. This demonstrates how important it is to get your recommended vaccine doses.
Immunocompromised People Should Get a Fourth Shot
The CDC recommends that moderately or severely immunocompromised individuals who received a two-dose mRNA COVID-19 vaccine get an additional primary vaccine dose at least 28 days after completing the second shot.
In addition to three primary doses, they should also receive a single booster shot three months after completing that third dose.
"Some people who are moderately or severely immunocompromised should receive a three-dose primary series and a booster dose because many of these individuals do not respond well to two or even three COVID-19 vaccine doses, and are thus less protected against variants such as Omicron," Moss said.
The mRNA COVID-19 vaccines are preferred, Kantor said. This goes for everyone, which includes immunocompromised individuals and the general population.
What This Means For You
If you are immunocompromised, you should get a booster dose after your first three doses. There is no evidence yet that non-immunocompromised individuals would need to get an additional booster shot to be protected.
Will Non-Immunocompromised People Need a Second Booster Dose?
Five months after completing a two-dose mRNA primary vaccine series, individuals aged 12 years and older who are not immunocompromised should get their booster dose. At present, there’s no evidence yet that a second booster shot is needed.
"Right now, most people do not need a second booster dose," Moss said. "Such an additional dose might be needed if there is evidence that people who received three doses are getting moderately to severely ill from COVID-19 or if there is a new variant that can escape much of our current immunity."
A study preprint published in medRxiv found that rates of confirmed infection and severe illness were lower after a fourth vaccine dose. However, preliminary results of two clinical trials also found that while a second booster dose does boost antibodies, it may not help prevent people from getting COVID-19.
More studies are needed to evaluate whether second booster doses are necessary. In addition, the virus will continue to mutate as long as the pandemic goes on, which will be another factor to consider.
"In the future, there may be a recommendation that people get an additional booster," Kantor said. "There are also efforts to make adjustments to the vaccines to make them more protective against the kind of adaptations that were observed in the Omicron variant."
If you have yet to receive your booster shot or primary vaccination series, you can visit vaccines.gov or text your zip code to 438829 to find vaccination providers near you.
"A large percentage of people are overdue for getting their recommended booster and should do so," Kantor said. "If it has been five or more months since your second shot, you are due for a booster."
The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.