Duration of immune protection of SARS-CoV-2 natural infection against reinfection in Qatar

Abstract

BACKGROUND: The future of the SARS-CoV-2 pandemic hinges on virus evolution and duration of immune protection of natural infection against reinfection. We investigated duration of protection afforded by natural infection, the effect of viral immune evasion on duration of protection, and protection against severe reinfection, in Qatar, between February 28, 2020 and June 5, 2022. METHODS: Three national, matched, retrospective cohort studies were conducted to compare incidence of SARS-CoV-2 infection and COVID-19 severity among unvaccinated persons with a documented SARS-CoV-2 primary infection, to incidence among those infection-naive and unvaccinated. Associations were estimated using Cox proportional-hazard regression models. RESULTS: Effectiveness of pre-Omicron primary infection against pre-Omicron reinfection was 85.5% (95% CI: 84.8-86.2%). Effectiveness peaked at 90.5% (95% CI: 88.4-92.3%) in the 7th month after the primary infection, but waned to ~70% by the 16th month. Extrapolating this waning trend using a Gompertz curve suggested an effectiveness of 50% in the 22nd month and <10% by the 32nd month. Effectiveness of pre-Omicron primary infection against Omicron reinfection was 38.1% (95% CI: 36.3-39.8%) and declined with time since primary infection. A Gompertz curve suggested an effectiveness of <10% by the 15th month. Effectiveness of primary infection against severe, critical, or fatal COVID-19 reinfection was 97.3% (95% CI: 94.9-98.6%), irrespective of the variant of primary infection or reinfection, and with no evidence for waning. Similar results were found in sub-group analyses for those ≥50 years of age. CONCLUSIONS: Protection of natural infection against reinfection wanes and may diminish within a few years. Viral immune evasion accelerates this waning. Protection against severe reinfection remains very strong, with no evidence for waning, irrespective of variant, for over 14 months after primary infection.

Duration of BA.5 neutralization in sera and nasal swabs from SARS-CoV-2 vaccinated individuals, with or without Omicron breakthrough infection

“…Infection-acquired immunity boosted with vaccination remained high more than 1 year after infection 27 . A study performed in Qatar reported that effectiveness of Pfizer vaccination against symptomatic BA.2 infection with two doses of Pfizer vaccine was negligible 28 , in agreement with our observation of a lack of detection Nabs against Omicron variants in sera from double vaccine recipients. The effectiveness of three doses of Pfizer, without or with previous infection was 52 % and 77%, respectively 28 .…”

“…A study performed in Qatar reported that effectiveness of Pfizer vaccination against symptomatic BA.2 infection with two doses of Pfizer vaccine was negligible 28 , in agreement with our observation of a lack of detection Nabs against Omicron variants in sera from double vaccine recipients. The effectiveness of three doses of Pfizer, without or with previous infection was 52 % and 77%, respectively 28 . Another report from USA indicated that vaccine effectiveness against COVID-19–associated hospitalization was higher during the BA.1 period than during the BA.2/BA.2.12.1 period 29 .…”

Risk of BA.5 infection in individuals exposed to prior SARS-CoV-2 variants

“…Hence, partial immune evasion can lead to a lower titre of neutralizing antibodies that, with a similar slope of decline, will tend to be faster in reaching a level of neutralizing antibodies unable to sustain protection from infection. The relationship between immune evasion and more rapid waning was well illustrated for omicron subvariants 10 . Still, the protection that we are calculating is the protection relevant for public health since infection with previous variants occurred at different times in the past.…”

Seroprevalence of anti-SARS-CoV-2 IgG antibodies in Tyrol, Austria: Updated analysis involving 22,607 blood donors covering the period October 2021 to April 2022

“…High levels of SARS-CoV-2 antibodies are associated with a lower infection risk and severe COVID-19 [1][2][3][4][5][6]. However, the level of protection is not assumed to be identical for all viral variants [7][8][9][10] and multiple factors contribute to the degree of individual immune response, such as age [11,12], sex [11,12], the variant which caused an infection [13,14], the severity of infection [15,16], vaccine products [17][18][19], and the inter-dose interval [20,21], among others. Furthermore, protection against SARS-CoV-2 infection diminishes over time as anti-SARS-CoV-2 antibodies wane [10,11,22].…”

“…However, the level of protection is not assumed to be identical for all viral variants [7][8][9][10] and multiple factors contribute to the degree of individual immune response, such as age [11,12], sex [11,12], the variant which caused an infection [13,14], the severity of infection [15,16], vaccine products [17][18][19], and the inter-dose interval [20,21], among others. Furthermore, protection against SARS-CoV-2 infection diminishes over time as anti-SARS-CoV-2 antibodies wane [10,11,22]. Therefore, continuous monitoring of the seroprevalence of antibodies is important to help appraising the latest immune status in the population.…”