The extensive analysis conducted by a team of American researchers, finds on 6.2 million people who have received at least one dose of the mRNA vaccine, that the association within 21 days of administration with serious adverse events, does not significantly outweigh similar reports. occurred between 22 and 42 days. Since over time the probability that other factors explain the causes increases, these results could indicate that for most of the reported cases there is no causal link with vaccines against the new Coronavirus, such as those from Pfizer and Moderna. Nonetheless, more studies will be needed before we get a clearer picture.
How the research was carried out
Since the first correlations between mRNA vaccines and reports of adverse events such as myocarditis have emerged, several research groups have been engaged in understanding whether these cases are indeed causally associated with inoculation. As mentioned, one way to shed some light on the issue is to compare reports up to 21 days after administration, with those recorded between 22 and 42 days.
The American study focuses on a total of 23 adverse events, starting from a base of more than 10 million people divided into eight vaccination plans underway in the United States. In both groups, subjects had received at least one dose of the vaccine between December 14, 2020 and June 26, 2021. The researchers collaborated with the US CDC, the FDA, and other federal agencies, including the Department of Human Affairs. veterans.
The adverse events taken into consideration are those recorded by Vaccine Adverse Event Reporting System (VAERS), which we remind, does not verify the causality of the reports received. In all, the researchers monitored 11.8 million doses, administered to a rather diverse population. Some evidence of a possible association between myocarditis and pericarditis was seen in younger adults. Nevertheless, the incidence in general does not significantly exceed that found after 22-42 days.
“The incidence of selected severe outcomes was not significantly higher from 1 to 21 days after vaccination compared to 22 to 42 days after vaccination for any of the same,” the researchers continue. was similar in demographic characteristics to the case and was in follow-up on the same day at the same site, avoiding bias that can result from variations in health care use during the pandemic, as well as daily variations (e.g. Sunday to Monday) “.
“All age analyzes combined did not reveal a significant association between myocarditis / pericarditis and mRNA vaccines […] Significant clustering within the first week after vaccination, especially after the second dose, provides further evidence for an association between mRNA vaccines and myocarditis / pericarditis in younger individuals. ‘
The limits of the study
This research, although it involves a large number of people, provides preliminary results. Further verification will be required. Statistical power was limited by several factors, especially when dealing with infrequent results. Variables that are not included in the research, such as previous vaccinations of other types, cannot be excluded.
After 21 days there is also a risk that certain adverse events have been underestimated and therefore do not fall within the reports. As usual, these kinds of studies cannot predict the long-term risks of vaccination. Finally, the study looked at cases followed by doctors, which may have kept several adverse events, such as anaphylaxis, off the radar, if for example the treatments had been administered in alternative settings.
Cover photo: qimono | MRNA vaccines.