Summer 2021 Widespread Uptick in New Covid-19 Cases:
naturally immune have negligible risk of reinfection
(7x lower risk than fully vaccinated)
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For May - June 2021,
“Natural infection
vs vaccination: Which gives more protection?”
reports the following results from the four medical databases that collectively, by state law, store the medical records for everyone in Israel:
7700 new Covid cases during the May-June 2021 uptick
~40% (i.e., 3,000+) of the new Covid cases were fully vaccinated
<1% (i.e., 72) of the cases were people known to have recovered from Covid
0.0578% (i.e., 3,000 / 5,193,499) of the fully vaccinated population were infected during the uptick
0.0086% (i.e., 72 / 835,792) of the Covid-recovered population were infected during the uptick
Both groups had very low probability, but those who were naturally immune were ~7x less likely to become infected during the uptick than those who were fully vaccinated.
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For June - Aug 2021,
“Comparing
SARS-CoV-2 natural immunity to vaccine-induced immunity…”
reports results obtained using a medical database for 2.5M people in Israel. Individuals who were unvaccinated but had a positive PCR test prior to Feb 28, 2021 were matched one-to-one with individuals who nad no prior positive PCR test but were fully vaccinated prior to Feb 28, 2021 based on age, gender and geographical area. In this matching, the unvaccinated with the previous positive PCR test had 7x lower risk of symptomatic infection and 5x lower risk of hospitalization during the June - August 2021 uptick than those who were fully vaccinated*.*The factors of 7x and 5x change to 27x and 8x, respectively, when the matching criteria is expanded to include the date of the pre-Feb 28 positive PCR test or second dose of the vaccine. Like these results, further evidence in the paper that those with natural immunity "gained additional protection" with a single dose of the BNT162b2 two-dose vaccine, was only found for those with a previous positive PCR test, rather than for those who were known to have previously recovered from a Covid infection. Results in the database for those who were known to have recovered from Covid are not given in this preprint.
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For July 11 – Aug 22, 2021, page 3 of the
Aug 26, 2021
Data Snapshot
for Dane County, Wisconsin, shows that the fully vaccinated (orange curve) are ~33% of the total new Covid cases (blue curve) during the summer 2021 uptick. This county doesn’t report results for those who have recovered from Covid, but the results for the fully vaccinated indicate how the results from Israel may hold qualitatively for other areas with 60-70% vaccination rate.