Breaking News: CDC revises guidance: all adults *should* receive booster if more than 6 months out from an mRNA Covid-19 vaccine.

A new statement upgrades previous guidance that all adults may receive boosters, if desired. The policy change also applies to Johnson & Johnson recipients.

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The Centers for Disease Control and Prevention has announced that all adults should receive a booster of a Covid-19 vaccine if more than 6 months out from completing the two-dose mRNA Covid-19 vaccine or 2 months out from the Johnson & Johnson vaccine. Previously, the guidance was that this group may receive a booster, if individuals felt they would benefit from it. Today’s news came in a statement from Dr. Rochelle Walensky, Director of the CDC.

It is unclear whether the change in booster guidance reflects any new as-yet unreleased laboratory, epidemiological, or clinical data about the Omicron variant, or whether the move is pre-emptive, based on concerns regarding the number of new mutations that the variant is known to have.

While the sheer number and the kinds of mutations that Omicron carries has worried many scientists, the technology to reliably predict how a virus’s behavior will change (including whether they can evade currently-available vaccines) based purely on genetic information does not exist.

One possible scenario is that Omicron’s mutations will make it more transmissible—making it easier for the virus to infect both unvaccinated people, previously infected and recovered people, vaccinated people, and even those boosted against Covid-19. But infections (i.e. case counts) themselves are not actually the results that matter, when you think about it; clinical outcomes are. The goal is to reduce and eliminate suffering. If some hypothetical asymptomatic virus with no long-term effects on our health and well-being suddenly infected all 7 billion humans on this planet, who would care? And if Omicron turns out to be more contagious than previous variants, but extraordinarily less virulent, that could actually be a great outcome, depending on the magnitude of the changes. Again, imagine 7 billion infections, but zero bad outcomes. (While I’ve seen this last theory floated as a possible outcome for Omicron, I think it’s way too optimistic to put much hope there.)

Given how our immune systems develop and maintain long-term protection after it sees a virus or a vaccine, it’s possible (and maybe even likely) that vaccine-induced protection against long-term effects, severe disease, hospitalization, or death in the face of Omicron will not change much, if at all. Again, if the CDC’s action today reflects any newly-obtained knowledge on this, it has certainly not been made public.

We should know if Omicron significantly escapes existing immunity in a matter of days-to-weeks. If it turns out that Omicron does not cause worse outcomes among the vaccinated, I hope the CDC will de-escalate today’s booster guidance.

Why? Because no matter what anyone tells you, boosting in wealthy nations deprives initial doses to poorer nations, maybe not today or tomorrow, but soon, and inevitably.

Meanwhile, there exists no circumstance in which boosting millions of people under the age of 50 or so could have the same impact as getting millions of initial doses into the unvaccinated would. While overcoming vaccine hesitancy (or refusal) remains a challenge, public health workers should literally be going door-to-door to make sure everyone who’s willing to be vaccinated is immunized immediately. That will remain true whether the variant is Alpha, Beta, Delta, Omicron, or whatever comes next.

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Special thanks to Dr. Céline Gounder for her expertise and comments.

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