In at least Quebec and Ontario we are entering the 6th wave. . . . The city of Ottawa monitors Covid viruses in sewage water and has set daily records for 5-6 days in a row now. Hospitalizations have increased but daily deaths are still in single figures for the province. Anybody with any sense is watching those numbers closely. Ontario has just recommended a 4th vaccine shot for those 60 and over.
Somewhat further south, we're also experiencing the beginning of a predicted spike in cases caused by the Omicron BA.2 subvariant; New York City and Washington, D.C. are the two most prominent epicenters. In the Maryland county where I live, about a 30-minute drive north of Washington, the case rate has been increasing fairly rapidly for two weeks now. However, we're not seeing a significant increase in deaths nor, as far as I can tell, hospitalizations.
The U.S. Food and Drug Administration has authorized a fourth dose (second booster) of the Pfizer-BioNTech and Moderna mRNA vaccines for people with compromised immune systems and anyone over 50. There has been considerable debate among the medical experts about whether another booster makes sense at this time, especially since all the current vaccines were designed to protect against the variants of the SARS-CoV-2 virus that were circulating in 2020 and early 2021 rather than the mutations that are infecting people now. (My wife and I decided to get the additional dose, anyway: we figured it might provide additional protection against severe disease and there seemed to be little reason to avoid it.)
A retrospective study of older patients in Israel that was published earlier this week in the
New England Journal of Medicine (attached) suggests that an extra Pfizer-BioNTech booster may provide increased short-term protection from infection as well as longer-lasting protection from severe disease compared to a three-dose regime. This came as a bit of a surprise precisely because the vaccine formulation was based on an old version of the coronavirus.
The omicron variant is genetically divergent from the ancestral SARS-CoV-2 strain for which the BNT162b2 vaccine was tailored. The results presented here indicate that as compared with three vaccine doses given at least 4 months earlier, a fourth dose provides added short-term protection against confirmed infections and severe illness caused by the omicron variant. The incidence rate for confirmed infection was lower by a factor of 2 and the rate of severe disease lower by a factor of 3 among persons in the fourth week after receiving the fourth dose than among eligible persons who did not receive the fourth dose.
Comparing the rate ratio over time since the fourth dose . . . suggests that the protection against confirmed infection with the omicron variant reaches a maximum in the fourth week after vaccination, after which the rate ratio decreases to approximately 1.1 by the eighth week; these findings suggest that protection against confirmed infection wanes quickly. In contrast, protection against severe illness did not appear to decrease by the sixth week after receipt of the fourth dose. More follow-up is needed in order to evaluate the protection of the fourth dose against severe illness over longer periods.
It seems likely that similar benefits would accrue to a fourth dose of the Moderna product, which is also based on mRNA vaccine technology.