As some people have now been vaccinated for more than half a year, evidence is pouring in about Covid vaccine efficacy. When evaluating vaccine efficacy, it is important to distinguish between efficacy against infection, symptomatic disease, and transmission versus efficacy against hospitalization and death. For infection and symptomatic disease, the COVID-19 vaccines are not as efficacious as hoped, with immunity gradually waning after a few months. For hospitalization and death, immunity is stronger, lasting for at least six months.
The gestalt of the findings implies that the infection explosion globally that we have been experiencing– post double vaccination in e.g. Israel, UK, US etc. –may be due to the vaccinated spreading Covid as much or more than the unvaccinated.
A natural question to ask is whether vaccines with limited capacity to prevent symptomatic disease may drive the evolution of more virulent strains? In a PLoS Biology article from 2015, Read et al. observed that:
“Conventional wisdom is that natural selection will remove highly lethal pathogens if host death greatly reduces transmission. Vaccines that keep hosts alive but still allow transmission could thus allow very virulent strains to circulate in a population.”
Hence, rather than the unvaccinated putting the vaccinated at risk, it could theoretically be the vaccinated that are putting the unvaccinated at risk, but we have not yet seen any evidence for that.
Here I summarize 16 studies and reports that shed light on vaccine induced immunity against Covid. They highlight the problems with vaccine mandates that are currently threatening the jobs of millions of people. They also raise doubts about the arguments for vaccinating children.
1) Gazit et al. out of Israel showed that “SARS-CoV-2-naïve vaccinees had a 13-fold (95% CI, 8-21) increased risk for breakthrough infection with the Delta variant compared to those previously infected.” When adjusting for the time of disease/vaccine, there was a 27-fold increased risk (95% CI, 13-57).
2) Ignoring the risk of infection, given that someone was infected, Acharya et al. found “no significant difference in cycle threshold values between vaccinated and unvaccinated, asymptomatic and symptomatic groups infected with SARS-CoV-2 Delta.”
3) Riemersma et al. found “no difference in viral loads when comparing unvaccinated individuals to those who have vaccine “breakthrough” infections. Furthermore, individuals with vaccine breakthrough infections frequently test positive with viral loads consistent with the ability to shed infectious viruses.” Results indicate that “if vaccinated individuals become infected with the delta variant, they may be sources of SARS-CoV-2 transmission to others.” They reported “low Ct values (<25) in 212 of 310 fully vaccinated (68%) and 246 of 389 (63%) unvaccinated individuals. Testing a subset of these low-Ct samples revealed infectious SARS-CoV-2 in 15 of 17 specimens (88%) from unvaccinated individuals and 37 of 39 (95%) from vaccinated people.”
4) In a study from Qatar, Chemaitelly et al. reported vaccine efficacy (Pfizer) against severe and fatal disease, with efficacy in the 85-95% range at least until 24 weeks after the second dose. As a contrast, the efficacy against infection waned down to around 30% at 15-19 weeks after the second dose.
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https://brownstone.org/articles/16-studies-on-vaccine-efficacy/