A comprehensive review of all available evidence from randomized controlled trials of COVID 19 vaccines through November 2021 concluded that most protect against infection and severe or critical illness caused by the virus.
The review, a collaboration of independent international experts, also found that there was little or no difference between the number of people who experienced serious side effects after vaccination compared to those who were not vaccinated.
The researchers, led by Isabelle Boutron, professor of epidemiology at Université Paris Cité and director of Cochrane France, analyzed published data from 41 randomized controlled trials of 12 different COVID-19 vaccines, involving 433,838 people from several countries. of the world. They assessed the certainty of the evidence and the risk of bias in the different studies.
The trials compared COVID-19 vaccines with placebo, no vaccine, or each other, and were published before November 5, 2021. Most trials lasted no more than two months.
The review found that the following vaccines reduced or probably reduced the risk of COVID-19 infection compared to placebo: Pfizer/BioNTech, Moderna, CureVac COVID-19, Oxford-AstraZeneca, Janssen, Sputnik V (Gam-COVID-Vac ), Sinopharm (WIBP CorV and BBIBP-CorV), Bharat (Covaxin), Novavax and Soberana 2 (Finlay-FR-2). The following reduced or probably reduced the risk of severe or critical illness: Pfizer/BioNTech, Moderna, Janssen, Sputnik V, Bharat and Novavax. Additionally, the Janssen and Soberana 2 vaccines likely decreased the risk of death from any cause. Very few deaths were recorded in all trials, so the evidence on mortality from the other vaccines is uncertain.
For most vaccines investigated, more people who had been vaccinated reported localized or temporary side effects compared to those who received no treatment or received a placebo. These included tiredness, headache, muscle aches, chills, fever and nausea. Regarding very rare side effects associated with some vaccines, such as thrombosis, the team found that the reporting of these events was inconsistent and that the number of events reported in the trials was very low.
Given the evidence of the effectiveness of these vaccines, researchers question whether it is ethical to conduct more placebo-controlled trials. They suggest that additional research compare the new vaccines with those already in use.
The current review analyzed data available through November 2021. The analyzes have since been updated and will continue to be made publicly available every two weeks by the COVID-NMA Initiative, which provides live mapping of COVID-19 trials. . A live and systematic review of clinical trials is available to both researchers and policy makers on the COVID-NMA platform. This allows the team to provide the most up-to-date evidence on which to base future research and decisions regarding the prevention and treatment of COVID-19.
Prof. Boutron said: “The evidence on COVID-19 vaccines is constantly changing and updating. Everything is moving so quickly that by the time the next Cochrane review is published, or other papers are published, the data will likely be out of date. There are more than 600 randomized vaccine trials currently registered, and about 200 of them are recruiting. COVID-NMA is the only initiative that continues to monitor developing evidence from trials and provides a platform for researchers to conduct their own analyzes through the metaCOVID tool on the website.
“Researchers, doctors and policymakers have to make very quick decisions about what to do to prevent and treat COVID-19. I hope this initiative will help them have access to the most up-to-date evidence on which to base their decisions.”
Authors’ conclusions Compared with placebo, most vaccines reduce, or probably reduce, the proportion of participants with confirmed symptomatic Covid‐19, and for some of them, there is high‐certainty evidence that they reduce severe or critical disease. There is likely to be little or no difference between most vaccines and placebo in terms of serious adverse effects. More than 300 registered RCTs are evaluating the efficacy of Covid‐19 vaccines, and this review is regularly updated on the COVID‐NMA platform (covid‐nma.com). Implications for practice Due to trial exclusions, these results cannot be extrapolated to pregnant women, people with a history of SARS-CoV-2 infection, or immunocompromised people. Most trials had short follow-up and were conducted before the emergence of variants of concern. Implications for research Future research should evaluate the long‐term effect of vaccines, compare different vaccines and vaccination schedules, evaluate the efficacy and safety of vaccines in specific populations, and include outcomes such as prevention of persistent Covid‐19. It is also essential to maintain continuous evaluation of the efficacy and effectiveness of vaccines against new variants of concern. |
