Expert review on global real-world vaccine effectiveness against SARS-CoV-2

Abstract

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 strati ed 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 speci c 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 signi cantly) 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 con rmed 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 bene t/risk pro les.-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 pro les, particularly against severe outcomes, and that are accessi...

Effectiveness of heterologous third and fourth dose COVID-19 vaccine schedules for SARS-CoV-2 infection during delta and omicron predominance in Thailand: a test-negative, case-control study

“… 24 The equivalent VE observed for the main booster vaccines used in Thailand is consistent with a recent global analysis of VE data demonstrating equivalence of mRNA and vector vaccines as two dose schedules against earlier variants of concern. 13 This strongly suggests that accelerating booster vaccinations and increasing coverage by using any vaccines available, particularly among those aged 60 and older or those with co-morbidities is a valid strategy.…”

“…The most widely used vaccines in real world studies showed high and equivalent effectiveness, especially against severe COVID-19 outcomes. 13 Some studies have reported higher neutralizing-antibody response with heterologous boosters as compared to homologous boosters. 14 , 15 , 16 , 17 However, there is limited data available on the real-world vaccine effectiveness (VE) of heterologous schedules, particularly against the newer omicron variants.…”

Heterologous third and fourth dose vaccine to reduce severity and mortality in COVID-19 patients during delta and omicron predominance: A cohort study in Chiang Mai, Thailand

“…Comparable protection from ChAdOx1 and P zer-BioNTech against infection has been previously reported. 10,16 Our data strongly suggests that accelerating the third and fourth dose vaccinations and increasing coverage by using any vaccines available, particularly among those aged 60 and older or those with comorbidities is an important strategy to optimize protection. Vaccination in addition to using personal protection measures such as wearing a mask, social distancing, and avoiding crowded settings, can help to reduce hospitalizations associated with omicron strain and, more importantly, mortality in the elderly or those with co-morbidities.…”

“…The initial clinical trials evaluated e cacy against early variants of concern, using homologous schedules, and high and equivalent effectiveness has been observed by the most widely used vaccines in real world studies, especially against severe COVID-19 outcomes. 10 Some studies have reported higher neutralizing-antibody response with heterologous boosters as compared to homologous boosters. [11][12][13] However, there is limited data available on the protective bene t of heterologous schedules, particularly against newer variants of concern.…”

Risk factors affecting COVID-19 vaccine effectiveness identified from 290 cross-country observational studies until February 2022: a meta-analysis and meta-regression

“…Although dozens of various reviews or meta-analyses have attempted to assess the effectiveness of vaccination against COVID-19 for different types of vaccines, [ 9 , 11 , 12 ], with regard to different coronavirus variants [ 9 , 11 , 13 , 14 ], risk groups [ 12 , 15 – 17 ], or the length of time after vaccination [ 15 , 18 ], no comprehensive study focused on the association of multiple factors with the vaccine effectiveness achieved has yet been published. Therefore, we decided to conduct a large meta-analysis extended with meta-regression referred to as “meta-COVANESS” (META-analysis/regression of COvid VAccine effectiveNESS) and to quantitatively evaluate the outcomes published during the first 2.5 years of immunization.…”