For Covid, a new wave and a new booster: Eric Topol

“The inconvenient truth is that we are going to experience a new BA.2 variant wave in the United States -— the magnitude of which remains uncertain -— and, this highlights the question of whether a 2nd booster (4th shot) would be useful,” Eric Topol writes over at his Substack. “In the past month, many countries in Western Europe have been going through a significant 2nd Omicron wave that is attributable to the BA.2 variant, some accompanied by a substantial rise in hospitalizations and deaths. The pattern varies by country, with some like Denmark, Netherlands and Austria having pronounced surges with BA.2 superimposed on BA.1, while others were more discrete. BA.2 waves in multiple European countries with different patterns. Omicron is a family of variants which includes BA.1, BA 1.1, BA.2, and others. Although they share many mutations, BA.2 is quite distinct from BA.1 with 8 unique mutations. Those 8 BA.2 mutations create a substantial antigenic distance from BA.1 —- how our immune system “sees” the spike protein. So there was concern that our vaccines would not be as effective against BA.2. Fortunately (yet, again, as I’ve previously written about, we’re very lucky) there is no drop-off between BA.1 and BA.2 with respect to vaccine effectiveness. For both, the protection vs infections starts out low, approximately 50%, and falls off substantially after a few months (which is why we had an enormous number of breakthrough infections in the first Omicron wave). But, importantly, the mRNA vaccines hold up well with a fresh booster against BA.1 or BA.2 vs hospitalizations and deaths. It has been estimated that about 40% of Americans were infected with the first wave of Omicron (with BA.1 or BA1.1) so there will be cross-reactive immunity/protection that should help reduce the severity of the wave, especially in people with hybrid immunity of vaccination and Omicron BA.1 infection.” Eric Topol, “A new wave and a new booster?” Substack.