Credit ACIP/CDC
#16,158
Although the HHS has already signaled their intention of begin offering COVID Booster Shots for ". . . all Americans beginning the week of September 20 and starting 8 months after an individual’s second dose." (see Joint Statement of Aug 18th ), Monday's ACIP meeting produced something less than a sweeping endorsement of the plan.
Instead, due to a lack of data on the effectiveness of a booster shot (which is not expected until October at the earliest), a far more modest booster plan was floated as a possibility.
The (above) excerpt from ACIP Slide #46 illustrates a possible recommendation by the Committee, which would target the highest risk individuals (LTCF residents, HCW, Adults > 65/75 years of age) for booster shots initially.
FDA approval of COVID Booster shots was granted in mid-August for a limited cohort of those who are immunocompromised (see FDA Authorizes Additional COVID Vaccine Dose for Certain Immunocompromised Individuals).
Complicating the decision for booster shots is the potential negative impact that may have on first-time vaccine uptake, and the calls by the WHO to ensure that the rest of the world has reasonable access to vaccines before rich nations begin giving out 3rd doses.
There is, of course, a lot at stake here.
If COVID vaccine breakthrough infections (and more importantly, hospitalizations and/or deaths) continue to increase, then healthcare delivery systems could be badly overburdened this winter, economies and the supply chain could suffer even more, and the faith in (and uptake of) the current vaccine could wane.
While very preliminary, and only covering span of a few weeks, we do have some data - published in a recent preprint by the Israeli government - on the initial effectiveness of booster shots, which began there in late July.
I've only published the link and a couple of excerpts. Those with a better grasp of higher math and statistics than I will want to follow the link and read it in its entirety.
I'll have a brief postscript when you return.
BNT162b2 vaccine booster dose protection: A nationwide study from Israel
Yinon M. Bar-OnϮ1 , Yair GoldbergϮ2 *, Micha MandelϮ3 , Omri Bodenheimer4 , Laurence Freedman5 , Nir Kalkstein6 , Barak Mizrahi6 , Sharon Alroy-Preis4 , Nachman Ash4 , Ron Milo&1, Amit Huppert&5,7
27/8/2021
Abstract
Background:
On July 30, 2021, a third (booster) dose of the Pfizer BNT162b2 vaccine was approved in Israel for individuals 60 years or older who had been fully vaccinated (i.e., received two doses) at least five months previously. Here, we estimate the reduction in relative risk for confirmed infection and severe COVID-19 provided by the booster dose.
Methods:
1,144,690 individuals aged 60y and older who were eligible for a booster dose were followed between July 30 and August 22, 2021. We defined dynamic cohorts where individuals initially belong to the ‘non-booster’ cohort, leave it when receiving the booster dose and join the ‘booster’ cohort 12 days later.
Rates of infection and severe COVID-19 outcomes per person-days at risk were compared between the cohorts using Poisson regression, adjusting for possible confounding factors.
Results:
Twelve days or more after the booster dose we found an 11.4-fold (95% CI: [10.0, 12.9]) decrease in the relative risk of confirmed infection, and a >10-fold decrease in the relative risk of severe illness. Under a conservative sensitivity analysis, we find ≈5-fold protection against confirmed infection.
Conclusions:
In conjunction with safety reports, this study demonstrates the effectiveness of a third vaccine dose in both reducing transmission and severe disease and indicates the great potential of curtailing the Delta variant resurgence by administering booster shots.
(SNIP)
Discussion
Our analysis shows that the booster dose of the BNT162b2 vaccine is highly effective in reducing the risk of both confirmed infection and severe illness. For example, if the combined effect of waning immunity and the Delta variant decrease the efficacy of a vaccine given >6 months ago against infection to ≈50%, as recent reports have suggested 16,17, and if the booster dose reduces the relative risk by 10-fold, it means that the probability of a booster vaccinated individual to being susceptible to infection would decrease to ≈5% (=50%/10) relative to unvaccinated individuals. This brings vaccine efficacy for booster-vaccinated individuals to ≈95%, similar to the original “fresh” vaccine efficacy reported against the Alpha strain 11,15 .
On average, severe illness develops ≈5 days after the first positive-sample date (Figure S5 in the Supplementary Appendix). Thus, the follow-up period in our data is short and confidence intervals for protection against severe disease are wide. Moreover, some individuals from the booster cohort for severe illness were likely infected prior to or immediately after receiving the booster, and this could lead to an underestimate in the inferred protection against severe illness.
(SNIP)
Understanding the protection gained by a booster dose is critical for policy making. On July 30, 2021, Israel was the first country in the world to make available a third dose of Pfizer BNT162b2 vaccine against COVID-19 to all people aged 60 or over who had been vaccinated at least five months previously. The results of such a policy are of importance for countries that seek strategies to mitigate the pandemic. Our findings give clear indications of the effectiveness of a booster dose even against the currently dominant Delta variant.
Ideally, we'd have several months of data - not weeks - but what is presented here is reassuring. In the opening days (> 12 days post booster shot), those with a 3rd shot appear to be as well protected (≈95%) as they were during the opening weeks following their initial round of vaccines.
How long this protection will last is something we won't know for months. And this study only deals with the Pfizer-BioNTech BNT162b2 vaccine.
Given the waning protection from the current vaccine, booster shots seem inevitable at this point. But exactly when they will be made available in the United States, and which cohorts will be prioritized to receive them first, remains to be hammered out.
