Vaccine type not critical for booster
Dear Dr. Roach: My wife and I are both in our late 60s. She has gotten three doses of the Pfizer vaccine, and I have gotten three doses of the Moderna, only because that was what was available when we got our first dose. Because of our age, we are considering getting a second booster dose. I know the recommendation is that either vaccine would be fine, but we’ve heard that since the two vaccines attack the virus differently, it might be a good idea to switch vaccines, so I would get the Pfizer and she would get the Moderna. What are your thoughts?
T.A.
Answer: It is indeed true that the Moderna and Pfizer vaccines, although very similar, do have different effects on the immune system. So there are some experts who recommend switching vaccines, just as you’ve suggested. Both vaccines are excellent at preventing severe disease and at raising antibodies, but the types of antibodies are a little different, and the effects on T-cells, the other main arm of the immune system, are also different. Most of the studies showing benefit have used boosters of the same type as the original series, so that’s also a perfectly good option. I took my fourth dose using the mRNA vaccine booster that was different from the last three I had gotten.
Initial studies looking at booster shots that have been optimized for the omicron variant have not shown better outcomes than the original vaccine, so I would not wait for a new formulation. Those who are in the group recommended for a fourth dose by the Food and Drug Administration (all adults who received the Johnson & Johnson vaccine, and anyone over 50 or with moderate to severe immunocompromise who had their third dose four or more months ago) should consider getting their vaccine now. I recommend those at highest risk, such as older adults (over 75, or in a nursing home), those with diabetes or those with immune deficiency such as organ transplant, get a vaccine now.
People who had a recent (within one year) confirmed COVID infection AND three doses of vaccine have a high level of protection and probably do not need a fourth dose.