As of November 2021, all adults ages 18 years and older are eligible to receive a single-dose COVID-19 vaccine booster shot. Those who initially received an mRNA vaccine (Pfizer/BioNTech or Moderna) can get their booster six months after their second shot, while those who received an initial dose of the Johnson & Johnson vaccine can get a booster dose two months after their initial vaccine.
The FDA and CDC are allowing individuals to select any COVID-19 vaccine (Pfizer/BioNTech, Moderna, or Johnson & Johnson) for their booster, either the same as (homologous) or different than (heterologous) their initial vaccine(s).
The FDA’s authorization was based, in part, on an NIH study that has not yet been peer reviewed or published. The study enrolled 458 adults who had received one of the three available COVID-19 vaccines at least three months earlier. The study participants each got a booster dose: one-third received a Pfizer/BioNTech booster, one-third received a Moderna booster, and one-third received a Johnson & Johnson booster. The researchers looked at immune response, side effects, and safety of the nine resulting vaccine combinations.
The researchers found that any vaccine-plus-booster combination substantially increased the level of neutralizing antibodies (antibodies that block the COVID virus from infecting cells). However, the increase was greatest in those who followed a Johnson & Johnson vaccine with an mRNA vaccine, in particular the Moderna vaccine. The increase in neutralizing antibodies was fourfold for Johnson & Johnson followed by a Johnson & Johnson booster; 35-fold for Johnson & Johnson followed by a Pfizer/BioNTech booster, and 76-fold for Johnson & Johnson followed by a Moderna booster. However, the Moderna booster dose used in this study contains twice as much antigen as the dose that the FDA has authorized for the Moderna booster. And, importantly, the study was not designed to directly compare vaccine regimens.
The study uncovered no new safety concerns, and side effects were similar to those people have experienced with COVID vaccinations across all primary and booster vaccines.
Given this and other evidence, it makes sense for most people who started with the Johnson & Johnson vaccine to consider boosting with an mRNA vaccine (Moderna or Pfizer/BioNTech). On the other hand, if you started with the Moderna vaccine, you might think twice before mixing and matching.
The FDA’s mix-and-match authorization makes booster shots less dependent on which vaccines are available and gives people more choices. For example, if you had an unpleasant reaction to your initial vaccine, you could choose a different one for your booster. Or, if you don’t remember which vaccine you started with, you can still get a booster.
The FDA and CDC did not recommend that particular groups of people seek out or avoid specific vaccines. However, it may be reasonable for young women to ask their doctor whether they should avoid a booster dose of the Johnson & Johnson vaccine, which is associated with increased risk of a rare but serious type of blood clot that has been more common in women ages 18 to 49 years. In addition, there has a been a higher-than-expected number of heart inflammation cases after vaccination with the mRNA COVID-19 vaccines in male adolescents and young men. Those who fall into that category may want to ask their doctor if they should avoid a Pfizer/BioNTech or Moderna booster.
Who can get a COVID-19 vaccine booster shot?
In November 2021, the FDA authorized, and the CDC endorsed, a single-dose COVID-19 vaccine booster for all adults ages 18 years and older. Those who initially received an mRNA vaccine (Pfizer/BioNTech or Moderna) can get their booster six months after their second shot, while those who received an initial dose of the Johnson & Johnson vaccine can get a booster dose two months after their initial vaccine.Individuals may select any vaccine for their booster, either the same (homologous) or different (heterologous) than their initial vaccine(s).
COVID-19 vaccines are effective, especially at preventing serious illness and death. However, evidence is showing that boosters for all adults, given at the appropriate time after your primary vaccination series, can help extend the protection and keep it at a higher level.
If you are eligible to get a booster shot, refer to find vaccine locations.