By Dr. Dhia Aldoori December 31, 2021
To the question
posed by ‘Anonymous’, whether I “believe” in booster vaccinations for COVID-19
my current stance is I have reservations on their administration. There are some
people with special circumstances (older age, immune system compromised, absence
of antibody response to initial vaccination) that may benefit from the booster.
There also may be a slight temporary boost in immunity from having a booster
shot as well. That said, we should focus our resources on vaccinating those who
are not vaccinated in the world, and this will help overcome this virus (among
other things decreasing the probability of new variants of SARS-Cov-2 arising).
My opinions have
been expressed in words which I find hard to improve upon in the viewpoint
published in Lancet in October 2021 which I pretty much agree with on almost
everything they wrote [1].
What follows is from their writing and notations from me are in orange:
“A new wave of COVID-19
cases caused by the highly transmissible delta variant (and now the omicron variant) is
exacerbating the worldwide public health crisis, and has led to consideration
of the potential need for, and optimal timing
of, booster doses for vaccinated populations.[2]
Although the idea
of further reducing the number of COVID-19 cases by enhancing immunity in
vaccinated people is appealing, any decision to do so should be evidence-based
and consider the benefits and risks for individuals and society. COVID-19
vaccines continue to be effective against severe disease, including that caused
by the delta variant. Most of the observational studies on which this conclusion is based are,
however, preliminary, and difficult to
interpret precisely due to potential confounding and selective reporting.
Even if boosting
were eventually shown to decrease the medium-term risk of serious disease, current vaccine supplies could save more
lives if used in previously unvaccinated populations than if used as boosters
in vaccinated populations.
Boosting could be
appropriate for some individuals in whom the primary vaccination, defined here
as the original one-dose or two-dose series of each vaccine, might not have induced
adequate protection—e.g., recipients of vaccines with low efficacy or those who
are immunocompromised[3].
Although the
benefits of primary COVID-19 vaccination clearly outweigh the risks, there
could be risks if boosters are widely introduced too soon, or too frequently,
especially with vaccines that can have immune-mediated side-effects (such as
myocarditis, which is more common after the second dose of some mRNA vaccines,[4]
or Guillain-Barre syndrome, which has been associated with
adenovirus-vectored COVID-19 vaccines[5]).
Current evidence
does not, therefore, appear to show a need for boosting in the general
population, in which efficacy against severe disease remains high. Even if
humoral immunity appears to wane, reductions in neutralising antibody titre do not necessarily predict
reductions in vaccine efficacy over time, and reductions in vaccine efficacy
against mild disease do not necessarily predict reductions in the (typically
higher) efficacy against severe disease. This effect could be because protection
against severe disease is mediated not only by antibody responses, which might
be relatively short lived for some vaccines, but also by memory responses and
cell-mediated immunity, which are generally longer lived.
Of interest,
reported effectiveness against severe disease in Israel was lower among people vaccinated either in January or April
than in those vaccinated in February or March, exemplifying
the difficulty of interpreting such data. A recent report on the experience in
Israel during the first 3 weeks of August 2021, just after booster doses were
approved and began to be deployed widely, has suggested efficacy of a third
dose (relative to two doses). Mean follow-up was, however, only about 7 person-days (less than
expected based on the apparent study design); perhaps more importantly, a very
short-term protective effect would not necessarily imply worthwhile long-term
benefit.[6]
…even in
populations with fairly high vaccination rates the unvaccinated are still the
major drivers of transmission and are themselves at the highest risk of serious
disease.[7]
If boosters
(whether expressing original or variant antigens) are ultimately to be used,
there will be a need to identify specific circumstances in which the direct and
indirect benefits of doing so are, on balance, clearly beneficial. any
decisions about the need for boosting or timing of boosting should be based on
careful analyses of adequately controlled clinical or epidemiological data, or
both, indicating a persistent and meaningful reduction in severe disease, with
a benefit–risk evaluation that considers the number of severe cases that
boosting would be expected to prevent, along with evidence about whether a
specific boosting regimen is likely to be safe and effective against currently
circulating variants.
The vaccines that are currently available are (relatively) safe, effective, and save lives. The limited supply of these vaccines will save the most lives if made available to people who are at appreciable risk of serious disease and have not yet received any vaccine. Even if some gain can ultimately be obtained from boosting, it will not outweigh the benefits of providing initial protection to the unvaccinated."
Bibliography:
[1] P. R. Krause et al., “Considerations
in boosting COVID-19 vaccine immune responses,” Lancet, vol. 398, no.
10308, pp. 1377–1380, Oct. 2021, doi:
10.1016/S0140-6736(21)02046-8/ATTACHMENT/99B4689E-FA37-476A-B30E-8D1E3B4E33BC/MMC1.PDF.
[2] E. Callaway, “COVID vaccine boosters:
the most important questions,” Nature, vol. 596, no. 7871, pp. 178–180,
Aug. 2021, doi: 10.1038/D41586-021-02158-6.
[3] N. Kamar, F. Abravanel, O. Marion, C.
Couat, J. Izopet, and A. Del Bello, “Three Doses of an mRNA Covid-19 Vaccine in
Solid-Organ Transplant Recipients,” N. Engl. J. Med., vol. 385, no. 7,
pp. 661–662, Aug. 2021, doi: 10.1056/NEJMC2108861.
[4] J. W. Gargano et al., “Use of
mRNA COVID-19 Vaccine After Reports of Myocarditis Among Vaccine Recipients:
Update from the Advisory Committee on Immunization Practices — United States,
June 2021,” MMWR. Morb. Mortal. Wkly. Rep., vol. 70, no. 27, pp. 977–982,
Jul. 2021, doi: 10.15585/MMWR.MM7027E2.
[5] “Statement of the WHO Global Advisory
Committee on Vaccine Safety (GACVS) COVID-19 subcommittee on reports of
Guillain-Barré Syndrome (GBS) following adenovirus vector COVID-19 vaccines.”
[Online]. Available:
https://www.who.int/news/item/26-07-2021-statement-of-the-who-gacvs-covid-19-subcommittee-on-gbs.
[Accessed: 31-Dec-2021].
[6] Y. M. Bar-On et al., “Protection
of BNT162b2 Vaccine Booster against Covid-19 in Israel,” N. Engl. J. Med.,
vol. 385, no. 15, pp. 1393–1400, Oct. 2021, doi: 10.1056/NEJMOA2114255.
[7] J. B. Griffin et al., “SARS-CoV-2
Infections and Hospitalizations Among Persons Aged ≥16 Years, by Vaccination
Status - Los Angeles County, California, May 1-July 25, 2021,” MMWR. Morb.
Mortal. Wkly. Rep., vol. 70, no. 34, pp. 1170–1176, 2021, doi:
10.15585/MMWR.MM7034E5.
