Past SARS-CoV-2 infection protection against re-infection: a systematic review and meta-analysis
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(22)02465-5/fulltext
Group 1
Past SARS-CoV-2 infection
Group 2
No past SARS-CoV-2 infection
Effectiveness of past infection by outcome
Infection
Symptomatic disease
Severe disease
Findings
High levels of protection from infection caused by
Alpha, beta, and delta variants
Lower levels of protection from infection caused by
Omicron BA.1 variant
Effectiveness against re-infection with the omicron BA.1 variant
Protection against reinfection, 45·3%
Protection against omicron BA.1 symptomatic reinfection, 44%
Protection against severe disease if reinfected with BA.1 is 88.9%
Protection from re-infection with ancestral strains
Alpha and delta variants
Declined over time
78·6% at 40 weeks
Protection against re-infection with omicron BA.1
Declined more rapidly
36·1% at 40 weeks
Protection against severe disease at 40 weeks if reinfected
Remained high for all variants
90·2% for alpha and delta variants
88·9% for omicron BA.1
Data suggests that the level of protection afforded by previous infection is at least as high, if not higher than that provided by two-dose vaccination using high-quality mRNA vaccines
As of June 1, 2022
COVID-19 pandemic had caused an estimated 17·2 million total deaths
6·88 million reported deaths
7·63 billion total infections and re-infections.
Between 15th November 2021 and 1st June 2022
3·8 billion people
46% of the global population,
have been infected by omicron and sublineages.
Understanding needed for
Predicting future potential disease burden
Designing policies, travel, access to venues
Informing choices, vaccines
Estimate protection from past infection
Systematically synthesise studies
65 studies from 19 countries
By variant
By time since infection
Up to Sept 31, 2022
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