Protection probability against SARS-CoV-2 Omicron variant BA.1, BA.2 and BA.5 in asympto- matic infection caused by prototype strain

ABSTRACT

Objective To estimate the protection probability against SARS-CoV-2 variant Omicron strains BA.1, BA.2 and BA.5 infection, symptomatic infection and severe disease outcomes in asymptomatic individuals infected with SARS-CoV-2 prototype strain previously. Methods Our previous study had shown that the dynamic change of neutralizing antibodies in asymptomatic individuals infected with the SARS-CoV-2 prototype strain. Based on our previous study, a peer–reviewed predictive model on the basis of logistic model was used to estimate the protection probability of asymptomatic individuals against Omicron strains BA.1, BA.2 and BA.5. We estimate the protection probability against infection, symptomatic infection and severe disease outcomes on 28, 51 and 261 days after confirmation. Results The protection probability against reinfection of Omicron variant strains BA.1, BA.2, and BA.5 on 28 days after confirmation were 30% (95% CI 16%–52%) , 23% (95% CI 15%–36%) and 8% (95% CI 4%–16%) respectively, while decreased to 9% (95% CI 3%–21%) , 6% (95% CI 3%–12%) and 2% (95% CI 1%–4%) on 261 days after confirmation. The protection probability against symptomatic infection of Omicron strains BA.1, BA.2, and BA.5 were 51% (95% CI 28%–80%) , 42% (95% CI 26%–67%) and 16% (95% CI 7% – 40%) respectively on 28 days after confirmation, while decreased to 16% (95% CI 7%–35%) , 12% (95% CI 7% – 22%) and 3% (95% CI 1% – 8%) on 261 days after confirmation. The protection probability against severe disease of Omicron strains BA.1, BA.2, and BA.5 were 91% (95% CI 72%–98%) , 88% (95% CI 70%–97%) and 66% (95% CI 35%–90%) respectively on 28 days after confirmation, while decreased to 60% (95% CI 35%–86%) , 51% (95% CI 32%–75%) and 22% (95% CI 10%–50%) on 261 days after confirmation. Conclusions Neutralizing antibodies induced in asymptomatic individuals infected with prototype strain could provide higher protection against Omicron strain BA.5 than Omicron strains BA.1 and BA.2. Among the three clinical outcomes, the protective probability against severe disease outcome was better, followed by symptomatic infection, and the protective probability against infection was poor. © 2023, Publication Centre of Anhui Medical University. All rights reserved.