March 31, 2023

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
  • 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 sub-lineages.

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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