• William Miller, MD

Booster Confusion

As COVID cases continue to decline in the US, while rising in some other areas in the world, a lot of attention is being placed on COVID vaccine boosters. Should we be doing a second booster shot? If so, who should get the second booster shot and when? Is it really necessary? How long is all this going to go on? If you are confused, then you are not alone.


The current recommendation by the CDC and the FDA is that all adults who have received the initial two shots of either the Moderna or Pfizer vaccine get a booster shot. These agencies also recommend that all people who got the one shot Janssen vaccine (Johnson & Johnson) get a booster. The booster can be either Moderna or Pfizer (but not Jansen) and it doesn’t matter which one you got originally.


Within the last week, both Pfizer and Moderna have asked the FDA to approve a second booster. This would mean that people would get a total of four shots. Pfizer is requesting it for all persons 65 and older, while Moderna is requesting it for all adults 18 and older with perhaps the caveat that it be preferentially targeted to those at higher risk. Since the beginning of the year, the CDC has been advising people who are moderately or severely immune compromised get a second booster shot. Moderate or severe immune deficiency is defined specifically as one of the following: actively undergoing cancer treatment, an organ transplant recipient including bone marrow transplant, hereditary immune deficiency syndromes, advanced AIDS or persons receiving high-dose immune suppression therapy for diseases like lupus or rheumatoid arthritis.


Evidence remains strong that being vaccinated is beneficial and that getting boosted is even more so. The CDC published a report on March 18th showing that during the recent Omicron surge in January people who were unvaccinated and contracted COVID were 12 times more likely to develop serious illness and require hospitalization than those people who contracted COVID but who were vaccinated with the original series followed by a booster. Further, those who only had the original series but were not boosted had a 4 times higher incidence of serious illness and hospitalization than those who were boosted. This supports the strong benefit to getting vaccinated and boosted.


The timing for the booster shot is at least 5 months after the second dose of Pfizer or Moderna, and at least 2 months as a second shot to the single Janssen. Most of the studies focus on the mRNA vaccines, which are Pfizer and Moderna in the US, as they have been shown to be more effective than the Janssen vaccine.


The research that supports another round of boosters, totaling four shots, comes out of Israel where they instituted a second booster shot at the end of last year for all adults. Initial results were encouraging and reported that there was a five-fold increase in circulating antibodies after the fourth shot. However, this does not necessarily mean that the protection it offers is five times higher since a jump in antibodies is always expected after a repeat exposure to an infection. More recent studies that have looked at how the Israeli population faired during the Omicron outbreak show that the benefit of a fourth shot was only marginal in otherwise healthy and younger adults. The primary benefit was in those over the age of 65 or who had other significant risk factors such as diabetes, kidney failure, heart disease, severe asthma and emphysema.


A study published in the prestigious journal Nature in February reporting on the Israeli data concluded that the first booster (third shot) was important, but that a second booster (fourth shot) only gave slight advantage beyond the first booster alone. Thus, it seems that chasing COVID with more and more boosters is probably not particularly beneficial.


As COVID transitions from a raging pandemic to a low to moderate level ongoing endemic, we may see the need for a yearly COVID shot like we do already for the flu. This will be important if COVID continues to mutate as it likely will.


To recap, vaccination including a booster is important for all adults. A second booster is probably not as important except if you have moderate or severe immune compromise, are above age 65 or have significant risk factors.

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