WHO update on boosters for all, during pregnancy, and primary series for kids. Here's what they got right and wrong.

The World Health Organization released a summary from a meeting of its expert panel entitled, “Roadmap for COVID-19 vaccination in the Omicron era.”

The report is not final, but as of now there are four big-ticket items.

1. Boosters-for-all no longer needed. High-risk people should get additional boosters.

The WHO will be recommending additional boosters (beyond initial booster doses) for high-risk people only. Also, the chair of the WHO’s committee said that very high risk groups might benefit from even more frequent boosters. This is in line with the data from Qatar (which I collaborated on), showing that even with the initial boosters, only high-risk groups benefitted with respect to severe disease; we also found that for infection, booster protection waned quickly, and that after 6 months, there were increased odds of reinfection, especially among immune-intact people, a phenomenon called “negative imprinting.”

The fact is that there were never great data showing booster benefit against severe disease or death for standard-risk younger adults. Only when all booster data from all demographics—young and old—were lumped together did it appear on the surface that everyone benefited from boosters across the age and risk spectrum.

Why? Because the booster benefit was so large in older and other high-risk populations that including younger healthy people in the analyses did not change the apparent overall vaccine effectiveness that much. Think of the booster as a jumbo jet flying a group of older and high-risk people around at 600mph. Loading the back of the plane with a bunch of young healthy people might slow the plane down to 500mph; sure, the plane still flies, but the young and healthy were statistical dead weight. While the WHO is technically only commenting on additional booster doses (rather than initial boosters), that’s a matter of practicality. They know the horse left the barn on the first boosters in many places and the main thing going forward is that high risk people need to be boosted at some interval (be it yearly or more often) while the rest of the population does not need a booster.

(Of note, I’m unclear as to why the WHO included frontline healthcare workers in the high-risk group. A high risk of infection is not the same as a high risk of a bad outcome. Seems to me that frontline workers should wait for bad waves before getting boosted, so that we are not sidelined during times when we are most needed.)

2. The highest-risk groups may need boosters more frequently than once per year.

The WHO now recognizes the need for more frequent boosters among the highest risk groups, including the immune-compromised. While the document does not specifically say this, the interview with Stat News implied that very high risk people might benefit from boosters every six months, similar to what Dr. Katelyn Jetelina and I wrote recently. So, this is good news.

Sidebar: I disagree with the idea that we should also offer boosters to the “worried well” more frequently, including this spring. As above, there can be a downside to over-boosting when the benefit is so small. We don’t know whether the bivalent booster also causes negative imprinting, so perhaps the downsides of boosting everyone will turn out to be less than what we saw with the Wuhan-only vaccine. In the future, Omicron-only boosters may address the backfire effect that clearly came into play after 6 months.

3. Pregnancy warrants boosting.

WHO will be recommending boosting during pregnancy, “if the last dose was given more than 6 months earlier.” This is almost exactly what I wrote with Dr. Sonja Rasmussen and Dr. Denise Jamieson (two experts on this topic) last November in an important ob-gyn journal. (We said more than 4 months, and I actually stand by that, though I’m open to revising if the WHO readout is compelling). This is smart because boosting protects mothers during a risky time and especially if the booster is given in the third trimester, the infant will be born with Covid-19 antibodies that might last several months, crucial during that fragile neonatal period. This recommendation is a major win.

4. Pediatric vaccine policy update (The WHO missed a key insight on infants).

For children, the WHO will recommend “considering the primary series and booster dose for healthy children and adolescents only within country context, including disease burden in this age group, cost-effectiveness, other health or programmatic priorities, and opportunity costs.” Anti-vaxxers are foaming at the mouth here, saying that the WHO has rejected Covid-19 vaccines for children. But that’s not what the WHO is saying. The question is not whether vaccines are safe and effective for children (that’s a yes), but rather whether the juice is worth the squeeze in all nations. If, for example, it costs $5,000,000 worth of vaccines to save one life of a 15-year old, a cold economic analysis might find this to be unsustainable for low-and-middle income countries. (That said, the ghost of Paul Farmer is spinning in his grave at this type of analysis).

However, as I’ve also written, there is one pediatric group that absolutely needs vaccination because their risk is so much higher than all other children (and even many adults): infants. Infants are unlikely to have been infected before (infection provides substantial protection from future severe disease, even without a vaccine) and they are also the most likely to be hospitalized of all children. Since Omicron showed up, infants have had even higher hospitalization risks than adults ages 50-64.

Overall impressions.

Overall, the WHO has to make policy that is actionable for its member nations, rich and poor. The new policies are not perfect, but in many ways, they’re trouble from the get-go. For example, in some nations, most kids have gotten Covid-19 already. For them, the spend on vaccines may not be worth it. In other place, kids remain immune-naive; For them (and certainly for infants), vaccines both save lives and probably money too.