The Lancet — COVID-19 vaccine efficacy and effectiveness—the elephant (not) in the room

Vaccine efficacy is generally reported as a relative risk reduction (RRR). It uses the relative risk (RR)—ie, the ratio of attack rates with and without a vaccine—which is expressed as 1–RR. Ranking by reported efficacy gives relative risk reductions of 95% for the Pfizer–BioNTech, 94% for the Moderna–NIH, 90% for the Gamaleya, 67% for the J&J, and 67% for the AstraZeneca–Oxford vaccines. However, RRR should be seen against the background risk of being infected and becoming ill with COVID-19, which varies between populations and over time. Although the RRR considers only participants who could benefit from the vaccine, the absolute risk reduction (ARR), which is the difference between attack rates with and without a vaccine, considers the whole population. ARRs tend to be ignored because they give a much less impressive effect size than RRRs: 1.3% for the AstraZeneca–Oxford, 1.2% for the Moderna–NIH, 1.2% for the J&J, 0.93% for the Gamaleya, and 0.84% for the Pfizer–BioNTech vaccines.

COVID-19 vaccine efficacy and effectiveness—the elephant (not) in the room

B-cell immune memory against Covid-19

I have posted many times about T-cell immunity against Covid-19. This new study (SARS-CoV-2 infection induces long-lived bone marrow plasma cells in humans), just published two days ago, confirms that “circulating resting memory B cells directed against the S protein were detected in the convalescent individuals” 11 months after first symptoms.

You can read more about it in this blog published on the Washington University School of Medicine website.

Covid-19: why children don’t get ill or infect others

Two publications came to my attention recently. The first one is Shared B cell memory to coronaviruses and other pathogens varies in human age groups and tissues:

Notably, prepandemic children also had class-switched convergent clones to SARS-CoV-2 and its viral variants, but not EBOV, at higher frequencies than adults. We hypothesize that previous HCoV exposures may stimulate cross-reactive memory, and that such clonal responses may have their highest frequencies in childhood.

These findings suggest that encounters with coronaviruses in early life may produce cross-reactive memory B cell populations that contribute to divergent COVID-19 susceptibilities.

The second one is Mesenchymal Stem Cells: The Secret Children’s Weapons against the SARS-CoV-2 Lethal Infection. I don’t understand enough about this one, but the hypothesis here is twofold:

First, the integrity presence of a stable regenerative state of pediatric and young individuals, mainly based on the support of active circulating stem cells; and, secondly, the active presence of the adaptive immune system characterized by a continuous turn-over of lymphocytes, NK and B lymphocytes.

Both studies, however, agree that

The SARS-CoV-2 infection in children appears to be an unusual event. Despite the high number of affected adult and elderly, children and adolescents remained low in amounts, and marginally touched.

Overall children are unaffected personally by this virus, and pose no threat to others, as they are far from being the initially-claimed main vector of transmission.

This also means children do not need to be vaccinated at all, let alone undergo the risk of an experimental drug only authorised for emergency use, and with no safety data available in that age group, nor with any long-term side effects known.