It is estimated that 18.2% of adults over the age of 18 have had the updated COVID-19 vaccine booster as of the first week of this month. That same percentage for children ages 6 months – 17 years is only 7.8%. No doubt there is greater vaccine hesitancy due to rampant vaccine disinformation and anti-vax campaigns. The intended audience for this blog post is not this group, but rather those who have not received the updated booster because they were not aware one was available or because they did not believe it was needed due to prior vaccination or infection.
A recent study (BNT162b2 XBB1.5-adapted Vaccine and COVID-19 Hospital Admissions and Ambulatory Visits in US Adults | medRxiv) looked at the efficacy of the updated XBB.1.5 Pfizer-BioNTech COVID-19 vaccine booster (2023-2024 formulation) in preventing the need for medically-attended care (office visit, urgent care visit, emergency room visit or hospitalization) for COVID-19 among adults a median of 30 days post-booster compared to a group that did not receive any updated booster regardless of prior infection or vaccination history. The median age of the study participants was 54 years. The study was conducted on patients cared for by a health system in California (Kaiser Permanente Southern California) between October 11 and December 10 of this year.
The adjusted odds ratios for the reduction in need for medically-attended care in the updated booster group were 0.37 for hospitalization and 0.42 for all other sites of care.
The most shocking finding was reported by the authors of this study in this statement: “Compared to the unvaccinated, those who had received only older versions of COVID-19 vaccines did not show significantly reduced risk of COVID-19 outcomes, including hospital admission.”
What does all this mean in plain English (at least as plain as I can make it)?
- Prior vaccination and/or infection does provide some degree of immunity for a period of time, but that protection wanes over time and is not durable (in other words, does not last for years). Thus, until new vaccines are available (there are some very promising ones undergoing clinical trials now), maintaining immune protection from moderate to severe disease will require updated boosters or alternatively repeated reinfections (however, my last blog piece and other prior ones have indicated why this is a foolish and dangerous approach).
- Because of rampant transmission among large populations of people across the world, including immunocompromised individuals, the SARS-CoV-2 virus is evolving through recombination (the swapping of genetic material between two or more SARS-CoV-2 viruses with different sequences in the same person) and mutations (changes that add to or subtract from the genetic sequence of the virus during the process of copying the genetic code in making new viruses in infected cells). Some of these genetic changes have resulted in newer forms of the SARS-CoV-2 virus being more immune evasive (i.e., being able to get around some of the body’s immune defenses, including antibodies). [I should note that SARS-CoV-2 is behaving in a way that is unprecedented. We have never had a virus be able to circulate in the general population infecting persons of all ages throughout the year for this many years, causing so many reinfections through immune evasion and evolve to the point that recombinant viruses have now been driving the pandemic for two years now. In view of this and other aspects of this virus that I have written about throughout the pandemic, I believe that the public’s confidence that repeated infections are of no significant concern to long-term health could very well end up being unjustified.]
- Because a higher proportion of the population received earlier vaccination, it would seem that some of the fall-off in booster uptake is not vaccine hesitancy, but rather a mistaken notion that boosters are not needed because of their prior vaccination and possibly because of the commonly- held notion that so-called “hybrid immunity” (the immunity resulting from a combination of prior vaccination and infection) is the ultimate immunity against reinfection.
- There is also a commonly-held belief that reinfections are always milder and/or the virus is evolving to become milder thus contributing to a sense of complacency about the need for subsequent boosters.
- While no doubt, there has been some degree of population immunity that has heretofore protected us from the high levels of deaths and hospitalizations that we previously saw in the Delta (fall 2021) and early Omicron (winter 2022) waves, this study is a warning, as well as what we are currently seeing in a number of countries recently with significant rises in hospitalizations and deaths, that the virus is evolving enough and our prior immunity is waning enough that relying on prior vaccinations and remote infections may no longer be sufficient protection against moderate and severe disease, and we could potentially see higher rates of disease and severe illness in the near future.
- The good news is that the newly updated booster is effective in significantly reducing the risk for moderate and severe COVID-19. The bad news is that a very small percentage of the population has received the new booster.
- My fear is that a lot of people travelled and gathered with others for the holidays believing that they had a lot more immune protection from moderate and severe disease than they really did. If so, we could see a significant rise in urgent care visits, emergency room visits, hospitalizations, and God-forbid, deaths over the next two to three weeks.
- If you have not received the newly updated COVID-19 booster and have not had COVID-19 in the past couple of months, it is not too late to get boosted. I would get it tomorrow, if I were you. And, the good news is that if you have concerns about the mRNA vaccines, you can get the Novavax booster, which is a rather “old-fashioned” type of vaccine that we have used for many years prior to this pandemic.
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