So-called ‘real world evidence’ firmly underpins the effectiveness and safety of mRNA vaccination against covid-19. These are three studies by Niklas Andersson et al. that used data from the Scandinavian countries and all of which have been published in The BMJ.
In the first study (n = 3.6 million people aged 18 and over) all mRNA booster regimens were found to be effective against severe covid-19 compared to primary vaccination alone. But heterologous boosters (i.e. vaccines from different brands) were slightly more effective than homologous boosters in preventing covid-19-related hospital admissions. In the second study In adults aged 50 years and older, the researchers looked at pre-specified side effects and the extent to which they occurred during the first 28 days after immunization. This concerned 1.7 million bivalent mRNA boosters. They found no increased risk of neurological, cardiovascular, autoimmune and other serious conditions. A post-hoc analysis did reveal a higher incidence of myocarditis in women: the absolute risk of this was approximately two to three extra cases per million booster doses. This risk is much lower than the risk of developing severe covid-19 in the absence of a booster or the risk of myocarditis due to covid-19.
In the third studyFinally, Andersson et al. compared the effectiveness of a fourth dose of the new mRNA bivalent covid-19 vaccines with a third dose alone (n = 2.5 million people aged 50 and older). That led to a relative risk reduction of 65 to 70 percent of covid-19-related hospitalization or death in the three months after the booster.
According to commentators Kristine Macartney and Bette Liu, these three studies have convincingly demonstrated that mRNA vaccines are protective and have an excellent ‘safety profile’.
2023-08-04 11:52:00
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