“The concern, of course, was decreased efficacy over time. “Waning immunity” is a known problem for influenza vaccines, with some studies showing near zero effectiveness after just three months, meaning a vaccine taken early may ultimately provide no protection by the time “flu season” arrives some months later. If vaccine efficacy wanes over time, the crucial question becomes what level of effectiveness will the vaccine provide when a person is actually exposed to the virus? Unlike covid vaccines, influenza vaccine performance has always been judged over a full season, not a couple months.
And so the recent reports from Israel’s Ministry of Health caught my eye. In early July, they reported that efficacy against infection and symptomatic disease “fell to 64%.” By late July it had fallen to 39% where Delta is the dominant strain. This is very low. For context, the FDA’s expectation is of “at least 50%” efficacy for any approvable vaccine.
Now Israel, which almost exclusively used Pfizer vaccine, has begun administering a third “booster” dose to all adults over 40. And starting 20 September 2021, the US plans to follow suit for all “fully vaccinated” adults eight months past their second dose.
Delta may not be responsible
Enter Pfizer’s preprint. As an RCT reporting “up to six months of follow-up,” it is notable that evidence of waning immunity was already visible in the data by the 13 March 2021 data cut-off.
“From its peak post-dose 2,” the study authors write, “observed VE [vaccine efficacy] declined.” From 96% to 90% (from two months to <4 months), then to 84% (95% CI 75 to 90) “from four months to the data cut-off,” which, by my calculation (see footnote at the end of the piece), was about one month later.
But although this additional information was available to Pfizer in April, it was not published until the end of July.
And it’s hard to imagine how the Delta variant could play a real role here, for 77% of trial participants were from the United States, where Delta was not established until months after data cut-off.”
Source: Does the FDA think these data justify the first full approval of a covid-19 vaccine? Peter Doshi, MD, August 2021
“Immunological studies have documented a steady decline of antibody levels among vaccinated individuals2. Long-term follow-up of vaccine trial participants has revealed a growing risk of breakthrough infection3. And health-care records from countries such as Israel, the United Kingdom and elsewhere all show that COVID-19 vaccines are losing their strength, at least when it comes to keeping a lid on transmissible disease.”
Source: COVID vaccine immunity is waning — how much does that matter?
“We know the efficacy of vaccination drops and that infection probability is very similar to that of the unvaccinated population after five or six months”
Prof. Eli Waxman of the Weizmann Institute of Science, Was Israel’s decision to give everyone COVID boosters a shot in the dark?
This is a sad reality:
