What’s the latest on second Covid vaccine boosters and should I recommend them to my adult patients?

On March 29, 2022, the CDC and the FDA approved second booster shots of Pfizer and Moderna Covid vaccines for everyone 50 years of age or older as well as people 12 years of age or older with moderate to severe immune deficiencies to be given at least 4 months following the first booster.1-3  This means a 4th dose of an mRNA vaccine for many adults and a 5th dose for those with moderate to severe immune deficiencies. 

Admittedly, these recommendations are made in the context of many uncertainties, including when the next Covid surge will arrive, what will be the predominant variant, and how will our immunity hold up if a surge occurs. 

Nevertheless, in discussing the merits of a 2nd booster, I would emphasize several “talking points”:

  • Covid hasn’t gone away with new cases still diagnosed daily, some still  requiring hospitalization, albeit at lower frequency than recent past. 
  • Our immunity against Covid wanes in the absence of boosters or natural infection.
  • SARS-CoV-2 has been unpredictable in its surges, as well as emergence of new variants with frequent changes in its virulence and ease of transmission. This means we don’t know when the next surge will hit us (summer, fall or later) and how the predominant variant will behave.
  • But let’s not get too hung up on surges! The fact is that as long as Covid is circulating around, maintaining a robust immunity against infection is the best way to avoid getting infected and the best way to do this is through boosters!
  • As more people go around without masks, the risk of unprotected exposure to SARS-CoV-2 is also likely to increase, particularly in indoor public gatherings.  Boosters may allow us the freedom to go maskless more often!
  • The risk of Long Covid even following mild infection is still real even between surges. This means even if we don’t get very sick from Covid, we are placing ourselves at risk of Long Covid. Remember, no Covid, no Long Covid!
  • Irrespective of whether it’s mild or even asymptomatic, Covid infection  can cause significant disruption in our lives, whether it be isolation at home, not being allowed to return to work or just the anxiety of having it or having passed it to others. This means that, at least currently, it’s premature to consider this virus as “just another respiratory virus.”  It’s impact on our everyday lives is still a lot different than typical respiratory viruses. 
  • mRNA vaccine boosters have been proven to be as safe as primary series. 
  • Last, but not the least, a preprint Israeli study involving volunteers 60 to 100 years old found a 78% reduction in mortality from Covid following a 2nd booster dose of Pfizer mRNA vaccine compared to those who only had 1 booster.This study has several limitations including self-selected volunteers who may already be at lower risk of Covid mortality due to their healthier lifestyle. Nevertheless, the data is very encouraging!

Ultimately, the decision to get a second booster, particularly during non-surge periods, will depend a lot on not only available facts but the individual’s threshold for acceptable risk of even mild disease, concern over transmission to others and more recently the cost of the vaccine, among other factors.  

Bonus Pearl: Did you know that each year there are plenty of uncertainties around which influenza A or B subtypes will be the predominant seasonal strain or what month they may surge but these questions never keep us from recommending the annual flu vaccine to the public as a means of reducing influenza cases and saving lives?   


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  1. D.A. Allows Second Covid Boosters for Everyone 50 and Older – The New York Times (nytimes.com)
  2. Coronavirus (COVID-19) Update: FDA Authorizes Second Booster Dose of Two COVID-19 Vaccines for Older and Immunocompromised Individuals | FDA
  3. CDC Recommends Additional Boosters for Certain Individuals | CDC Online Newsroom | CDC
  4. Arbel R, Sergienko R, Friger M, et al. Second booster vaccine and Covid-19 mortality in adults 60-100 years old. Preprint, posted March 24, 2022. 24514bba-2c9d-4add-9d8f-321f610ed199.pdf (researchsquare.com)

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis, Massachusetts General Hospital, Harvard Catalyst, Harvard University, their affiliate academic healthcare centers, or its contributors. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!


What’s the latest on second Covid vaccine boosters and should I recommend them to my adult patients?

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