Natural immunity…


Date: February 24, 2023

01) LINK

“Past SARS-CoV-2 infection protection against re-infection: a systematic review and meta-analysis

Group 1

Past SARS-CoV-2 infection

Group 2

No past SARS-CoV-2 infection

Effectiveness of past infection by outcome


Symptomatic disease

Severe disease


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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