Jun 29, 2021 11:34:47 AM | 4 Min Read

COVID Vaccine Update: Understanding Immunity and Potential for Boosters

COVID Vaccine Update: Understanding Immunity and Potential for Boosters

As of mid June, at least 173.8 million people have received one or both doses of a coronavirus vaccine in the U.S. This includes more than 143.9 million people who have been fully vaccinated. A significant milestone is that 50% of eligible Americans have received at least one dose, affording protection against COVID-19.

Overall, national vaccination rates crested in mid-April at an average of 3.3 million doses per day and have fallen in recent weeks to a rolling average of under 2 million per day. All adults have been eligible for vaccines since April. What has changed is 17 million children, as young as 12, are now qualified for a coronavirus vaccine as well, following the Food and Drug Administration emergency authorization granted for the Pfizer-BioNTech two-shot regimen for adolescents.

But what about immunity? Is the protection afforded by the vaccines short-lived? Will receiving an annual booster shot be required? For our Confidio clients, boosters could add to plan costs if annual boosters become as normal as seasonal influenza vaccines.


COVID-19 utilization across the Confidio book-of-business through June 14, 2021

Let’s take a look at what two recent studies have reported to try and address the question of boosters:

  • Immunity to the coronavirus lasts at least a year, possibly a lifetime, improving over time, especially after vaccination, according to the two studies 1.
  • Both seem to allude that most people who have recovered from COVID-19 and who were later vaccinated will not need a booster.
  • The studies also seem to indicate that vaccinated people who were never infected most likely will need a booster, as will a minority who were infected but did not produce a robust immune response.

Each report observed individuals exposed to the coronavirus about a year earlier. Cells that retain a memory of the virus persist in the bone marrow and may churn out antibodies whenever needed, according to the study published in the journal Nature2.

Another study posted online at BioRxiv3, a site for biology research, found that these so-called memory B cells continue to mature and strengthen for at least 12 months after the initial infection.

These two studies may ease anxieties that immunity to the virus is short-lived. In fact, memory B cells produced in response to infection with SARS-CoV-2 and enhanced with vaccination are so potent that they thwart even variants of the virus, negating the need for boosters, according to Michel Nussenzweig, an immunologist at Rockefeller University in New York4.

However, this protection derived from vaccines alone may still require boosters as the immune memory is likely to be organized differently after immunization, compared with that following natural infection. So, in laymen’s terms, it causes people who have not had COVID-19 and received immunization may eventually need a booster shot, Dr. Nussenzweig said.

But what about people who have indicated they will not get a COVID-19 vaccination because they were previously infected? Would they be considered immune? Unfortunately, there is no assurance that such immunity would be potent enough to protect such an individual long-term, especially if you factor in the appearance of variants of the coronavirus.

In summary:

  • The studies imply that people who have recovered from COVID-19 and who have later been vaccinated will continue to have extremely high levels of protection against emerging variants, even without receiving a vaccine booster down the line.
  • Conversely, the studies agreed that immunity is expected to differ in people who have never had COVID-19. Combating a live virus is different from responding to a single viral protein introduced by a vaccine.


  1. https://www.washingtonpost.com/graphics/2020/health/covid-vaccine-states-distribution-doses/?itid=lb_coronavirus-what-you-need-to-read_4
  2. https://www.nature.com/articles/s41586-021-03647-4
  3. https://www.biorxiv.org/content/10.1101/2021.05.07.443175v1.abstract
  4. https://www.nytimes.com/2021/05/26/health/coronavirus-immunity-vaccines.html

Topics: COVID-19, Vaccine

Related Posts

COVID Vaccine Update

With three COVID-19 vaccines approved under Emergency Use Authorization (EUA), what is the latest...

Read More

The COVID Vaccine Derby: A Guide to the Top Contenders

The Race To A New Normal: A COVID-19 Vaccine Pipeline Update

The medical community has been...

Read More

FDA Authorized Booster for People With Weakened Immune Systems

Estimate impact of high-risk COVID population

BackgroundAs expected, on August 12, the U.S. Food...

Read More