C19 Weekly Briefing Supplement on the importance of maintaining high circulating levels of neutralizing antibodies through vaccine boosters.
The new wave of the pandemic is being driven by Delta which bypasses prior immunity at a higher rate than any previous variant. How is Delta managing to do this? It appears likely that some combination of mutations allow it to escape key neutralizing antibodies while affording it the ability to generate more viral copies (viral titers among people infected with Delta are 1,000 times higher than those of people infected with the original strain of the virus), combined with timing. People have the highest level of neutralizing antibodies shortly after getting vaccinated or infected and then those levels wane gradually over months until they are low enough to allow for breakthrough infections. It is likely that those who were vaccinated or infected several months ago have less immune protection against getting infected than those who were vaccinated or got infected more recently.
The process of getting C19 starts with exposure–a person inhales viral aerosols that stick to mucous membranes in the nose, nasopharynx, or lungs. This is called colonization. If someone has high levels of circulating neutralizing antibodies in the immune system of the mucous membranes (called the "MALT"), they can kill off the virus before it penetrates into the body's interior to cause an infection. This is what happens in most people who were recently vaccinated. However, as circulating neutralizing antibody titers wane over time, the MALT has fewer soldiers to keep colonization contained and this allows breakthrough infections to occur.
There are now sufficiently ample data showing that an additional shot of vaccine boosts circulating neutralizing antibodies to levels much higher than those seen after completion of the initial vaccination regimen. This should provide those who get booster shots with much stronger protection against getting infected (lots of neutralizing antibodies circulating in the MALT). And there have been no reports of adverse events from receiving a third shot of mRNA vaccine or a second shot of Janssen vaccine. So what's the delay and why are so many experts still not recommending booster shots across the board? Three reasons have been given:
The focus of most public health and infectious disease experts has been on the acute viral period of C19. That's largely because, while some other infections can cause long-term health consequences, most do not, and most doctors by training are concerned about preventing severe illness and death. But C19 has shown itself to be different from other common RTIs in so many ways (it's airborne, it's more contagious, it's more deadly, it shape-shifts more quickly than expected, etc.) and the fact that it causes such a high degree of chronic and potentially chronic illness is just one more distinguishing feature of this novel virus. It is not unreasonable to be concerned that in the end, the second and third phases of C19 will wind up taking a larger toll on society than the (sometimes deadly) first phase. If boosters were available today, I'd take one immediately.
943. Iceland recommends booster shots for all citizens who got Janssen at 8 weeks post-vaccination.
944. Moderna seeks authorization of the first variant-specific booster shot; but it's tuned to Beta, not Delta.
945. Pfizer submits data from Phase I clinical trials on booster doses which they now recommend for the general population. Boosters triggered the production of significantly higher levels of circulating neutralizing antibodies against Delta.
946. Dr. Fauci: "Everyone will need a booster shot."
947. Israel is now doing booster shots for all persons 50 and over and for all healthcare workers.
948. Biden Administration to approve booster shots for most Americans at 8 months post-vax, beginning with healthcare workers.