Emerging variants of concern (VOCs) prompted a group of researchers to evaluate the impact of various allocation strategies of COVID-19 vaccines and antiviral so that the pandemic exit strategy could be customized based on the risks and preferences of jurisdictions in the East Asia and Pacific region (EAP) to improve its efficiency and effectiveness.

Vaccine efficacies were calculated utilizing the titer distributions of 50% plaque reduction neutralization test (PRNT50), supposing that PRNT50 titers of primary vaccination reduced by 2-10 folds due to antibody waning and emergence of VOCs, and an additional dose of vaccine would boost PRNT50 titers by 3- or 9-fold. Further, an existing SARS-CoV-2 transmission model was employed to assess the outcomes of vaccine allocation strategies with and without the use of antivirals for symptomatic patients.

The Findings were-

Increasing primary vaccination coverage appeared to be the prime contributing factor in reducing the total and peak number of COVID-19 hospitalizations, particularly when population vaccine coverage or vaccine uptake among older adults was low. 

Providing antivirals to 50% of symptomatic infections reduced total and peak hospitalizations by 10-13%. 

The effectiveness of an additional dose of vaccine was greatly dependent on the immune escape potential of VOCs and antibody waning, but lesser on the boosting efficacy of the additional dose.

Thus, increasing primary vaccination coverage should be prioritized in designing allocation strategies of COVID-19 vaccines and antivirals against emerging VOCs in the EAP region. Heterologous vaccination with any available vaccine as the additional dose may be also planned.

Source- The Lancet Regional Health - Western Pacific. 2022;21.https://doi.org/10.1016/j.lanwpc.2022.100389.