How Long Does COVID-19 Vaccine Immunity Last?

What experts know about immunity after vaccination and whether booster shots will be necessary.

Clinical trials and real-world conditions have proved that vaccines protect against COVID-19. But the question remains: How long will vaccine immunity last?

In light of recent studies that individuals who are moderately to severely immunocompromised may not build an adequate level of immunity from two doses of the mRNA vaccines, the U.S. Food and Drug Administration (FDA) approved a third dose of the Pfizer or Moderna vaccines for that population. The FDA has also authorized a booster shot for people over 65 or in an at-risk population who had received the Pfizer vaccine. The booster for those individuals would come at least six months after their second injection.

To learn more about this evolving issue, Health Matters spoke with Dr. Sharon Chacko, medical director at the Farrell Community Health Center at NewYork-Presbyterian’s Ambulatory Care Network, medical director of COVID-19 immunizations in the Division of Community and Population Health, and an assistant professor of medicine at Columbia University Vagelos College of Physicians and Surgeons, about vaccine immunity and the recommendation for booster shots.

Dr. Sharon Chacko

Dr. Sharon Chacko

Health Matters: What do we know about how long immunity lasts after vaccination for COVID-19?
Dr. Chacko: Initially, we knew immunity lasted at least six months after vaccination, because the first trials had six months of data at that time. Health officials have continued to monitor data, and with the rise of variants, such as the highly contagious Delta variant, they are keeping a close eye on breakthrough infections and waning immunity.

There is some encouraging news. In late August, the CDC got new data that the vaccines continued to provide strong protection against severe disease even after the Delta variant had become the dominant variant in the United States. The data showed that the Pfizer, Moderna, and J&J vaccines remained highly effective at preventing hospitalizations from April to July.

How do researchers assess immunity?
The participants who are in these studies are monitored regularly after vaccination. They receive regular blood tests to have their antibody levels checked and are also checked for breakthrough infections — meaning people who are infected with COVID-19 even after vaccination. Using those two factors and others, researchers are able to obtain more information about the expected duration of immunity.

Some sources state that immunity may be higher in people who have had COVID-19 and later got vaccinated. Is this true?
There has been some suggestion of that. The idea is that people who have had COVID-19 build a natural antibody response and then subsequently, when they are vaccinated, that vaccination builds upon the initial immunity to create an even larger immune response.

That being said, the CDC recommends everyone — even people who were infected with COVID — get vaccinated, because we do not know how long one is immune after recovering from COVID.

What are booster shots and how do they work?
For some vaccines, as time goes on, immunity decreases, and so a booster shot refreshes the immune response. An example of this is the tetanus shot, which you have to get every 10 years to ensure continued immunity.

” In late August, the CDC got new data that the vaccines continued to provide strong protection against severe disease even after the Delta variant had become the dominant variant in the United States.”

— Dr. Sharon Chacko

What is the difference between a “booster dose” and an “additional dose”?
A booster dose is given to people when it is likely that the immune response to a primary vaccine series has decreased over time.

In the case of those with immunosuppression, the concern is that the immune systems did not mount an adequate response after the initial series, so an additional dose is recommended for people who are moderately to severely immunocompromised in order to improve their immune response.

The FDA has officially authorized a third dose of the COVID-19 vaccine for people with moderate to severe immunosuppression. The CDC recommends that individuals from that population who completed either the Pfizer or Moderna COVID-19 vaccine series receive an additional dose of mRNA vaccine at least 28 days after completion of the second dose in order for them to mount a larger immune response. People should talk to their healthcare provider about their medical condition, and whether getting an additional dose is appropriate for them.

What do we know for sure?
Here’s what we know:

  • Vaccines are highly effective.
  • Areas with higher vaccination rates have lower incidence of COVID-19 and a decreased rate of COVID-19 hospitalizations and death.
  • Areas with higher vaccination rates also have a lower incidence of variant strains, keeping everyone safer.

One thing we can all do is get vaccinated and encourage the people in our lives to also get vaccinated. Vaccination provides individual immunity, and as more people are vaccinated, we stop the spread of COVID-19, which means fewer opportunities for the virus to mutate, and thus slow the emergence of new variants.

Sharon M. Chacko, M.D., is a family medicine physician and the medical director at the Herman “Denny” Farrell, Jr. Community Health Center at NewYork-Presbyterian’s Ambulatory Care Network and an assistant professor of medicine in the Center for Family and Community Medicine at Columbia University Vagelos College of Physicians and Surgeons. Dr. Chacko has been a medical lead for NewYork-Presbyterian’s COVID-19 vaccination efforts and served as medical director at the vaccination site established by NewYork-Presbyterian at The Armory. She is now medical director of COVID-19 immunizations in the Division of Community and Population Health.

On July 27, the CDC updated guidance for fully vaccinated people given new evidence on the transmissibility of the Delta variant, adding a recommendation for fully vaccinated people to wear a mask in public indoor settings in areas of substantial or high transmission. Fully vaccinated people may choose to wear a mask in these settings regardless of the level of transmission, particularly if they are immunocompromised or at increased risk for severe disease from COVID-19, or have someone in their family who is.