Safety and effectiveness of vaccines against COVID-19 in children aged 5-11 years: a systematic review and meta-analysis.

BACKGROUND: To date, more than 761 million confirmed SARS-CoV-2 infections have been recorded globally, and more than half of all children are estimated to be seropositive. Despite high SARS-CoV-2 infection incidences, the rate of severe COVID-19 in children is low. We aimed to assess the safety and efficacy or effectiveness of COVID-19 vaccines approved in the EU for children aged 5-11 years. METHODS: In this systematic review and meta-analysis, we included studies of any design identified through searching the COVID-19 L·OVE (living overview of evidence) platform up to Jan 23, 2023. We included studies with participants aged 5-11 years, with any COVID-19 vaccine approved by the European Medicines Agency-ie, mRNA vaccines BNT162b2 (Pfizer-BioNTech), BNT162b2 Bivalent (against original strain and omicron [BA.4 or BA.5]), mRNA-1273 (Moderna), or mRNA-1273.214 (against original strain and omicron BA.1). Efficacy and effectiveness outcomes were SARS-CoV-2 infection (PCR-confirmed or antigen-test confirmed), symptomatic COVID-19, hospital admission due to COVID-19, COVID-19-related mortality, multisystem inflammatory syndrome in children (MIS-C), and long-term effects of COVID-19 (long COVID or post-COVID-19 condition as defined by study investigators or per WHO definition). Safety outcomes of interest were serious adverse events, adverse events of special interest (eg, myocarditis), solicited local and systemic events, and unsolicited adverse events. We assessed risk of bias and rated the certainty of evidence (CoE) using the Grading of Recommendations Assessment, Development and Evaluation approach. This study was prospectively registered with PROSPERO, CRD42022306822. FINDINGS: Of 5272 screened records, we included 51 (1·0%) studies (n=17 [33%] in quantitative synthesis). Vaccine effectiveness after two doses against omicron infections was 41·6% (95% CI 28·1-52·6; eight non-randomised studies of interventions [NRSIs]; CoE low), 36·2% (21·5-48·2; six NRSIs; CoE low) against symptomatic COVID-19, 75·3% (68·0-81·0; six NRSIs; CoE moderate) against COVID-19-related hospitalisations, and 78% (48-90, one NRSI; CoE very low) against MIS-C. Vaccine effectiveness against COVID-19-related mortality was not estimable. Crude event rates for deaths in unvaccinated children were less than one case per 100 000 children, and no events were reported for vaccinated children (four NRSIs; CoE low). No study on vaccine effectiveness against long-term effects was identified. Vaccine effectiveness after three doses was 55% (50-60; one NRSI; CoE moderate) against omicron infections, and 61% (55-67; one NRSI; CoE moderate) against symptomatic COVID-19. No study reported vaccine efficacy or effectiveness against hospitalisation following a third dose. Safety data suggested no increased risk of serious adverse events (risk ratio [RR] 0·83 [95% CI 0·21-3·33]; two randomised controlled trials; CoE low), with approximately 0·23-1·2 events per 100 000 administered vaccines reported in real-life observations. Evidence on the risk of myocarditis was uncertain (RR 4·6 [0·1-156·1]; one NRSI; CoE low), with 0·13-1·04 observed events per 100 000 administered vaccines. The risk of solicited local reactions was 2·07 (1·80-2·39; two RCTs; CoE moderate) after one dose and 2·06 (1·70-2·49; two RCTs; CoE moderate) after two doses. The risk of solicited systemic reactions was 1·09 (1·04-1·16; two RCTs; CoE moderate) after one dose and 1·49 (1·34-1·65; two RCTs; CoE moderate) after two doses. The risk of unsolicited adverse events after two doses (RR 1·21 [1·07-1·38]; CoE moderate) was higher among mRNA-vaccinated compared with unvaccinated children. INTERPRETATION: In children aged 5-11 years, mRNA vaccines are moderately effective against infections with the omicron variant, but probably protect well against COVID-19 hospitalisations. Vaccines were reactogenic but probably safe. Findings of this systematic review can serve as a basis for public health policy and individual decision making on COVID-19 vaccination in children aged 5-11 years. FUNDING: German Federal Joint Committee.

From standard systematic reviews to living systematic reviews.

Systematic reviews (SRs) have become a central tool for evidence-based health care over the last 30 years. The number of SRs being published has increased steadily. However, concerns have been raised regarding the duplication of work, methodological flaws and the currency of many systematic reviews, also in the context of the COVID-19 pandemic. Living systematic reviews (LSRs) offer a new approach to updating systematic reviews, particularly in high-priority research fields that face the challenge of dynamically evolving and sometimes uncertain evidence. Continual updates serve to ensure that LSRs remain current and methodologically rigorous. As a new element of the evidence ecosystem, LSRs can inform living guidelines and recommendations, user-adapted formats, decisions at the patient and system level as well as gaps in primary research.

Three out of four published systematic reviews on COVID-19 treatments were not registered and one-third of those registered were published: a meta-research study.

OBJECTIVES: The aim of this study is to describe (1) registered and (2) published systematic reviews (SRs) on COVID-19 treatments, and to analyze (3) the proportion of publications among registered SRs and (4) the proportion of registrations among published SRs. STUDY DESIGN AND SETTING: This meta-research study (CRD42021240423) is part of CEOsys (http://www.covid-evidenz.de/). Two reviewers identified protocols in PROSPERO (registered January 2020 to September 2020) and SRs published as preprint or peer-reviewed article in L·OVE (Living OVerview of the Evidence) COVID-19 (by May 2021). SRs of all types assessing COVID-19 treatments in humans were included. RESULTS: We included 239 PROSPERO protocols and 346 SRs published in L·OVE. In both samples, the affiliation of the corresponding author with an Asian institution, standard SR as review type, and meta-analysis as synthesis method were the most frequent characteristics. Living SRs made up ≤10%. A total of 71 of 239 (29.7%) PROSPERO protocols were published as SR by February 2022, that is, after at least 17 months of follow-up (25 of 71 as preprints, 35.2%). In L·OVE, 261 of 346 (75.4%) SRs published by May 2021 were not registered in PROSPERO. CONCLUSION: Overall, one-third PROSPERO protocols were published and three-fourth published SRs were not registered. We strongly encourage authors to register and publish their SRs promptly to reduce research waste and to allocate resources efficiently during the pandemic and beyond.

Characteristics of registered and published systematic reviews focusing on the prevention of COVID-19: a meta-research study.

OBJECTIVE: We investigated characteristics of systematic reviews (SRs) assessing measures to prevent COVID-19 by (1) identifying SR registrations in Prospective Register of Systematic Reviews (PROSPERO), (2) identifying published SRs in COVID-19 Living Overview of the Evidence (L-OVE) and (3) estimating the proportion of PROSPERO registrations published as full SR between 8 and 16 months after registration. STUDY DESIGN: This meta-research study is part of the German CEOsys project, www.covid-evidenz.de. We searched PROSPERO entries registered between 1 January 2020 and 31 August 2020, and we searched COVID-19 L-OVE for published SRs (search date: 5 May 2021) focusing on measures to prevent COVID-19 and SARS-CoV-2 transmission. The two samples were screened for eligibility and key characteristics were extracted and summarised. RESULTS: Of 612 PROSPERO registrations, 47 focused on prevention and were included. The preventive measures included public health interventions (20), followed by personal protective equipment (10), vaccinations (9) and others (8). In total, 13 of 47 (28%) PROSPERO registrations had been published as full SR (as preprint only (6), as peer-reviewed article only (6), as preprint and peer-reviewed article (1)). Median time between PROSPERO registration and publication was 5 months for peer-reviewed SRs and 2 months for preprints.Of the 2182 entries identified in COVID-19 L-OVE, 51 published SRs focused on prevention and were included. Similar to the PROSPERO sample, most published SRs focused on public health interventions (21). The number of included primary studies ranged between 0 and 64 (median: 7). Nine published SRs did not include any studies because of a lack of primary studies. CONCLUSION: Considering the urgent information needs of policymakers and the public, our findings reveal the high-speed publication of preprints and lack of primary studies in the beginning of the COVID-19 crisis. Further meta-research on COVID-19 SRs is important to improve research efficiency among researchers across the world. PROSPERO REGISTRATION NUMBER: CRD42021240423.