Expert Review of Global Real-World Vaccine Effectiveness Against SARS-CoV-2
Authors: CHUENKITMONGKOL Sunate , SOLANTE Rontgene , BURHAN Erlina , CHARIYALERTSAK Suwat , CHIU Nan-Chang , DO-VAN Dung , HUSIN Masliyana , HWANG Kao-Pin , KIERTIBURANAKUL Sasisopin , KULKARNI Prasad S. , LEE Ping-Ing , LOBO Rommel Crisenio , NGHIA Cao Huu , ONG-LIM Anna , SIVASAMPU Sheamini , SUAH Jing Lian , TOK Peter Seah Keng , THWAITES Guy 
Published: June 2022

IntroductionCOVID-19 vaccines have been highly effective in reducing morbidity and mortality during the pandemic. While primary series vaccination rates are generally high in Southeast Asian (SEA) countries, various factors have limited the rollout and impact of booster doses.Areas coveredWe reviewed 79 studies in the publicly available International Vaccine Access Center (IVAC) VIEW-hub platform on vaccine effectiveness (VE) after primary immunizations with two-dose schedules. VE data were reported for SARS-CoV-2 infection, COVID-19-related hospitalizations and deaths, and stratified across variants of concern (VOC), age, study design and prior SARS-CoV-2 infection for mRNA vaccines (BNT162b2, mRNA-1273 and combinations of both), vector vaccines (AstraZeneca, AZD1222 “Vaxzevria”) and inactivated virus vaccines (CoronaVac).Expert opinionThe most-studied COVID-19 vaccines provide consistently high (>90%) protection against serious clinical outcomes like hospitalizations and deaths, regardless of variant. Additionally, this protection appears equivalent for mRNA vaccines and vector vaccines like AZD1222, as supported by our analysis of local Asian and relevant international data, and by insights from SEA experts. Given the continued impact of COVID-19 hospitalizations and deaths on healthcare systems worldwide, encouraging vaccination strategies that can reduce this burden is more relevant than attempting to prevent broader but milder infections with specific variants, including Omicron.Article highlights - VE was high and comparable for both AZD1222 and mRNA vaccine types (91%-93%) in protecting against hospitalization and death from COVID-19, regardless of age.- VE against symptomatic infections trended higher (though not significantly) for mRNA-based vaccines compared to AZD1222.- Waning of VE since time of vaccination was observed for symptomatic infections but was limited for serious COVID-19 outcomes. A sub-analysis of studies with comparative arms evaluating the VE of different vaccines in the same settings also confirmed these observations for all VOC assessed, with all vaccines conferring a high level of protection against serious outcomes.- For Omicron, there is limited comparative data within the IVAC dataset, however, expert review of emerging data suggests that VE against all outcomes is lower for all COVID-19 vaccines, than for the Delta variant.- Data from the UK indicate that VE improves with a booster dose and that VE continues to be very similar, irrespective of the type of vaccine used.- Importantly, all COVID-19 vaccines evaluated here have favorable benefit/risk profiles.- Although many SEA countries have high rates of primary vaccination, there are still challenges to achieving high booster dose coverage. The results of this analysis suggest that the most effective way to achieve vaccine booster targets, particularly in resource-limited settings, would simply be to consider any vaccines which have good safety and comparable effectiveness profiles, particularly against severe outcomes, and that are accessible and optimal for the local situation.- This review reinforces the value of real-world evidence to support efforts advocating for the completion of primary series and booster vaccinations where appropriate, especially to restore VE against emerging VOC such as Omicron. However, data gaps still persist, given the lag between the emergence of new variants, updated vaccine schedules and VE data to inform their impact.