New mRNA vaccine technologies may offer 94-95 % efficacy. What an achievement of 21st century science!
On the other hand, good old natural immunity provides 100 % protection from symptomatic COVID-19, as shown in the study of 12.5k healthcare workers below. https://twitter.com/BallouxFrancois/status/1343547659081154566">https://twitter.com/BallouxFr...

Another large study finds precisely the same thing: 100 % natural immune protection from symptomatic COVID-19 within 6 months of first infection. https://www.journalofinfection.com/article/S0163-4453(20)30781-7/fulltext">https://www.journalofinfection.com/article/S...

What could provide lasting protection? Repeated exposure.
Tissue resident memory T cell presence “required airway vaccination and antigen persistence in the lung, as non-respiratory routes of vaccination failed to support long-term lung TRM maintenance.” https://www.nature.com/articles/s41385-020-0309-3">https://www.nature.com/articles/...

One more study. While it claims “only” 94 % protection efficacy, the benchmark (PCR+) is much stricter than what was used in vaccine studies (symptomatic infection). The authors report one hospitalization in the previous infection group (could be >99 %). https://www.journalofinfection.com/article/S0163-4453(21)00010-4/fulltext">https://www.journalofinfection.com/article/S...

“late asymptomatic RT-PCR re-positivity does occur after COVID-19, even 6 months later, and does not necessarily represent new infectionhttps://abs.twimg.com/emoji/v2/... draggable="false" alt="❗️" title="Rotes Ausrufezeichen" aria-label="Emoji: Rotes Ausrufezeichen">, despite the prolonged time interval elapsed and the negativity of subsequent RT-PCR tests since the first diagnosis” https://www.journalofinfection.com/article/S0163-4453(21)00152-3/fulltext">https://www.journalofinfection.com/article/S...