Uncovering the secrets of natural COVID-19 immunity

A comprehensive review and meta-analysis published in The Lancet found that innate immunity to severe COVID-19 (hospitalization and death) was robust against all variants, including Omicron BA.1, in previously infected individuals. It proves to be long-lasting. Protection against reinfection, symptomatic disease, and severe disease is at least equivalent to her two doses of mRNA vaccine. However, prior infection with a pre-omicron variant compromised innate immune defenses against reinfection with omicron BA.1.

According to the Lancet study, natural immunity to severe viruses is COVID-19 Potent and long-lasting against all variants in previously infected individuals. However, protection against Omicron BA.1 reinfection is reduced if he was previously infected with Omicron infection. Researchers stress that vaccination remains the safest way to gain immunity.

• The largest review and meta-analysis evaluating the degree of variant protection after COVID-19 infection and how durable that protection is against different variants, including 65 studies from 19 countries.
• In people with at least one previous COVID-19 infection, innate immunity against severe illness (hospitalization and death) was strong and persistent for all variants (88% at 10 months post-infection). that’s all).
• Prior infection with a pre-Omicron variant significantly reduced innate immune protection against reinfection with Omicron BA.1 (36% at 10 months post-infection).
• Researchers say we need to recognize natural immunity in people recently infected with COVID-19, but vaccination should not be discouraged as it is the safest way to gain immunity. I warn you.

A systematic review published in 2018 found that people with previous COVID-19 had an 88% lower risk of hospitalization or death for at least 10 months compared to people with no previous infection. and according to a meta-analysis, lancet.

Analyzes also showed that the level and duration of protection against reinfection, symptomatic disease, and severe disease varied among ancestral, alpha, delta, and Omicron BA.1 variants. This study did not include data on infections from Omicron XBB and its substrains.

“Vaccination is the safest way to confer immunity, but conferring natural immunity must be weighed against the risk of serious illness and death associated with initial infection,” said lead author Dr. Stephen Lim of the Institute for Health Metrics and Evaluation (IHME) said:and University of WashingtonSchool of Medicine, USA.

IHME co-author Dr. Caroline Stein explains: This includes previously uninfected or unvaccinated populations, as well as those who have been infected or last vaccinated more than 6 months ago. We need to have a complete picture of an individual’s immune profile, considering both immunity and vaccination status. “

Since January 2021, several studies and reviews have reported on the effectiveness of past COVID-19 infections in reducing the risk of reinfection and how immunity declines over time. . However, there is no comprehensive assessment of how long the protection lasts after natural infection and to what extent that protection persists against different subspecies.

To provide more evidence, the researchers conducted a review and meta-analysis of all previous studies comparing reduced risk of COVID-19 in unvaccinated individuals. SARS-CoV-2 Reinfection in unvaccinated individuals with no previous infection by September 2022.

65 studies from 19 countries (Austria, Belgium, Brazil, Canada, Czech Republic, Denmark, France, India, Italy, Netherlands, Nicaragua, Norway, Qatar, Scotland, South Africa, Sweden, Switzerland, United Kingdom, United States) were included. I was. We also assess the efficacy of past infections by outcome (infection, symptomatic disease, severe disease), variant, and time since infection. Studies examining innate immunity in combination with vaccination (i.e., hybrid immunity) were excluded from the analysis.

Immunity declines over time

Analysis of data from 21 studies reporting time from infection from pre-omicron variants estimated protection against reinfection from pleomicron variants to be approximately 85% at 1 month, indicating that this dropped to about 79% in 10 months. Protection from pleomicron variant infection against reinfection from the Omicron BA.1 variant was low (74% at 1 month) and declined rapidly to 36% at approximately 10 months.

Nonetheless, an analysis of five studies reporting severe illness (hospitalization and death) found that protection remained high overall for 10 months: 90% in ancestral, alpha, delta and omicron 88% for BA.1.

Six studies that specifically assessed protection against Omicron substrains (BA.2 and BA.4/BA.5) suggested that protection was significantly reduced if previous infection was pre-Omicron variants. rice field. However, a higher level of protection was maintained when the previous infection was Omicron.

“The weak cross-variant immunity of the Omicron variant and its sublineages reflects mutations that make it easier than other variants to evade constructed immunity,” said IHME co-author Hasan Nassereldine, Ph.D. I’m here. “Limited data on innate immune defenses from the omicron subspecies and their substrains are ongoing, especially as it is estimated that 46% of the world’s population was infected between November 2021 and June 2022. Further studies also needed to assess the innate immunity of the new mutants and examine the protection offered by the combination of vaccination and natural infection.”

The researchers noted some limitations of their study and cautioned that the number of studies examining Omicron BA.1 variants and their substrains, as well as numbers from Africa, is generally limited. I’m here. Furthermore, limited data were available beyond 10 months after the initial infection. They also note that some information, such as past infection status and hospitalizations, may be measured differently or imperfectly, biasing estimates of protection.

In a linked comment, Professor Sheryl Cohen of the National Institute of Infectious Diseases, who was not involved in the study, said: 19 Vaccine Policy. By September 2021, the global SARS CoV-2 seroprevalence was estimated at 59%, with wide variability in the proportion of immunity induced by infection or vaccination in different settings. Seroprevalence in Africa was estimated at 87% in December 2021, mainly as a result of infection. High levels of immunity are a key factor in the low levels of severity observed in infections caused by the emerging His Omicron subvariant. As the epidemiology of SARS-CoV-2 shifts to a more stable circulation pattern associated with high levels of immunity, studies of the burden and cost of SARS-CoV-2 infection and risk groups for severe disease It is necessary to guide rational vaccination policies and decisions. On priorities in relation to other vaccine-preventable diseases. “

Reference: “Historical SARS-CoV-2 Infection Protection Against Reinfection: A Systematic Review and Meta-Analysis,” COVID-19 Prediction Team, 16 February 2023, Available here. lancet.
DOI: 10.1016/S0140-6736(22)02465-5

This research was funded by the Bill & Melinda Gates Foundation, J. Stanton, T. Gillespie, J. and E. Nordstrom. The research team included researchers from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington School of Medicine.