A Southeast Asia 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: April 2022

BackgroundCOVID-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.MethodsTo objectively review the evidence for vaccine effectiveness (VE), we extracted data from 79 studies identified in the publicly-available International Vaccine Access Center (IVAC) VIEW-hub platform reporting VE after a primary immunisation with two-dose schedules for three important clinical outcomes. We evaluated VE after primary immunisation against SARS-CoV-2 infection, and COVID-19-related hospitalisations and deaths for the most widely reported vaccines, stratified across variants of concern (VOC), age, study design and prior SARS-CoV-2 infection. The majority of studies evaluated mRNA vaccines (58 BNT162b2 studies, 34 mRNA-1273 studies and 14 combinations of both) and vector vaccines [25 COVID-19 Vaccine AstraZeneca, Vaxzevria studies (AZD1222)] with only 5 other studies available (all CoronaVac). For simplicity, mRNA studies were grouped together irrespective of which vaccine was used. VE point estimates were presented graphically with pooled means and confidence intervals were compared using standard t-tests for expert discussion.Findings VE was high and equally effective for both AZD1222 and mRNA vaccines types (91%-93%) in protecting against hospitalisation 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. Importantly, data from the United Kingdom (UK) indicates 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 favourable benefit/risk profiles.Interpretation Our review of the robust real-world VE data collated through the IVAC VIEW-hub platform confirms that the most studied COVID-19 vaccines in this database provide consistently high (>90%) protection against serious clinical outcomes like hospitalisations and deaths, and regardless of variant. Additionally, our observation that this protection appears equivalent for mRNA vaccines and vector vaccines like AZD1222 is supported by our analysis of local Asian and relevant international data, and by insights from SEA experts. Given the continued impact of COVID-19 hospitalisations 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.What this study adds This additional context 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.