How effective are previous SARS-CoV-2 infections and hybrid immunity against Omicron breakthrough infections?

In a recent article published in lancet infection, investigators conducted a systematic review and meta-regression study to determine the breadth and duration of protective immunity conferred by previous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and hybrid immunity. It was conducted. They evaluated the evidence in this data for infection by SARS-CoV-2 Omicron.

Background

A majority of the world’s population acquired hybrid immunity after mass vaccination, followed by the emergence of the SARS-CoV-2 Omicron (B.1.1.529) variant, whose immune evasion ability caused reinfection.

About research

For this study, the researchers searched several databases, including MEDLINE, European PubMed Central, and clinicaltrials.gov, between 1 January 2020 and 1 June 2022. A cross-sectional study using keywords related to SARS-CoV-2, its previous infection, reinfection, presence of antibodies, and hybrid immunity.

Researchers have evaluated several outcomes related to hybrid immunity. For example, hybrid immunity compared to previous infection only, vaccination only, and hybrid immunity with lower vaccine doses. They also determined the risk of bias in the studies covered in the study analysis. In addition, using log-odds random-effects meta-regression, he estimated the breadth of immunoprotection against omicron at 1-month intervals across the study period.

The analysis targeted studies examining immune protection against Omicron reinfection, where the exposure group consisted of individuals previously infected with SARS-CoV-2 variants or hybrid immunity. Control groups included non-immune, previously infected or vaccinated individuals. Researchers determined Omicron infection by whole-genome sequencing or based on the prevalence period of variants per the Global Initiative for Avian Influenza Data Sharing (GISAID) database.

Investigation result

Both previous SARS-CoV-2 infection and hybrid immunity provided adequate protection against Omicron infection, which quickly waned. Moreover, previous episodes of COVID-19 provided greater and sustained protection against hospitalization or severe his COVID-19 than vaccination alone. Conversely, individuals with hybrid immunity showed more durable protection against all her COVID-19 outcomes, highlighting the importance of vaccinating previously infected individuals.

Because infection-induced protection against breakthrough infection wanes rapidly, and vaccination improves the durability of this protection. Vaccination is therefore a credible intervention to prevent severe outcomes of COVID-19 and reduce her post-COVID-19 complications, including cardiovascular and neurological sequelae.

Furthermore, the findings of this study highlight the need to optimize the timing of COVID-19 primary vaccination series and individual booster doses. As already known, individuals previously infected with SARS-CoV-2 or who had a breakthrough infection after initiation of a primary COVID-19 vaccination series had a boost time compared to non-immune individuals. is different. It is reasonable for him to delay the booster by 6 months. Because those who were previously infected or fully vaccinated enjoy naturally higher immunity to severe her COVID-19.

More importantly, the researchers advocated conducting a serosurvey to estimate the seroprevalence of previous infections at the population level. This is because the ideal number of vaccinations and intervals between vaccinations are largely different in different population-level settings. This should be the cornerstone of immunization policies in many countries, especially those not using inactivated COVID-19 vaccines. Another example is countries that have used only SARS-CoV-2 spike (S) protein-based vaccines.

In such countries, anti-nucleocapsid diagnostic assays can identify previously infected individuals and inform booster recommendations. does not apply.

The authors warn that changing the COVID-19 vaccination program may reduce vaccine uptake. Therefore, it is best to keep vaccine deployment simple. Additionally, the World Health Organization (WHO) recommends not delaying or ruling out immunizations based on past infections. Additionally, boosting may be beneficial before COVID-19 incidence increases, especially in winters when the SARS-CoV-2 variants that caused past infections are unknown. As is widely known, the prevalence of COVID-19 remains highly underestimated in most countries during the pandemic.

Conclusion

The results of this study revealed substantial persistence of hybrid immunity to help inform the timing of vaccination programs in populations with high past SARS-CoV-2 prevalence.

Future studies should evaluate the protective effects of hybrid immunity against hospitalization and critical illness. These two outcomes will drive most COVID-19 policy decisions. It is therefore important to know how much immunity induced by hybrid immunity declines over time, especially amid the emergence of novel SARS-CoV-2 variants of concern. Precise quantification helps inform the need and timing of booster vaccinations.