A new report published today by CDC researchers revealed the possible side effects of the mRNA COVID-19 vaccine after one and second doses.
An analysis of side effects following COVID-19 vaccination with mRNA vaccines in the United States indicates that the majority of side effects were modest and subsided after one day.
According to a new study published in the journal Lancet, 92 percent (313,499/340,522) of reported side effects for more than 298 million vaccine doses administered between December 2020 and June 2021 were not serious, and less than 1 percent of v-safe participants sought medical care after vaccination.
Two mRNA COVID-19 vaccines – Pfizer-BioNTech (BNT162b2) and Moderna (mRNA-1723) – were approved for emergency use in the United States in December 2020. Both vaccines had two major doses and had good safety profiles in clinical trials, with mild side effects such injection site soreness, fatigue, and headache being the most common side effects.
As with all vaccines in the United States, anybody can report adverse effects using the Vaccine Adverse Event Reporting System (VAERS), a long-standing reporting system managed jointly by the US CDC and the FDA. Any event occurred after receiving a vaccine can be reported to VAERS by US individuals, their healthcare providers, or vaccine manufacturers. There are three types of reports: non-serious, serious, and death. The CDC-managed v-safe system was created expressly for the COVID-19 immunization campaign and comprises smartphone-based surveys emailed daily for the first week after vaccination (and at longer intervals in the months after) to track adverse events.
Between December 2020 and June 2021, this study looked at available VAERS and v-safe self-reported data following both doses of either the Pfizer-BioNTech or Moderna mRNA vaccines. Over 298 million doses of mRNA vaccines were delivered over the study period (132 million Moderna and 167 million Pfizer).
Over 340,000 complaints of side effects were received by VAERS, with over 313,000 (92 percent) of them classified as non-serious, including headache (64,064/340,522 or 20 percent), fatigue (52,048/340,522 or 17 percent), fever (51,023/340,522 or 16 percent), chills (49,234/340,522 or 16 percent), and pain (47,745/340,522 or 15 percent).
Shortness of breath (4,175/340,522 or 15 percent) was the most common of the more than 22,000 (6.6 percent) serious side effects reported. Approximately 4500 (1.3 percent) of the 340,522 adverse events reported to VAERS over the study period were deaths, with more than 80 percent of these deaths occurring in patients aged 60 and up.
Because COVID-19 vaccinations have been approved for emergency use, healthcare practitioners are required to record all deaths that occur after receiving the vaccine, regardless of whether there is a causal link. The authors of the study point out that cause death reports did not reveal any noteworthy tendencies.
“The rapid pace at which COVID-19 vaccines were administered under emergency use, especially among older populations, was unprecedented. Due to their age, this group already has a higher baseline mortality rate than the general population and our results follow similar patterns of deaths rates for people in this age group following other adult vaccinations,” says study author Dr David Shay.
Over half of the roughly 8 million v-safe participants reported local (4.6 million) and systemic (3.6 million) reactions following vaccination, with the latter happening more frequently than the first.
The most common side effects were recorded the day after immunization and were nearly all moderate, with the following being the most common:
- Fatigue (2,295,205/6,775,515 or 34 percent after dose one, 3,158,229/5,674,420 or 56 percent after dose two),
- Headache (1,831,471/6,775,515 or 27 percent after dose one, 2,623,721/5,674,420 or 46 percent after dose two),
- And injection site pain (4,488,402/6,775,515 or 66 percent after dose one, 3,890,848/5,674,420 or 69 percent after dose two).
After dose two (1,821,421/5,674,420, or 32 percent), more v-safe reports of being unable to work, perform normal activities, or seek medical attention were reported than after dose one (808,963/6,775,515, or 12 percent). After either vaccine dose, less than 1% of individuals (56,647 after dose one and 53,077 after dose two) sought medical attention.
Study author Dr Tom Shimabukuro (US CDC) adds: “These data are reassuring that reactions to both mRNA vaccines are generally mild and subside after one or two days—confirming reports from clinical trials and post-authorization monitoring.”
This study has some drawbacks, according to the authors. To begin with, the VAERS system is based on self-reporting and does not represent the full population. This also means that, while it can look for potential safety signals, it can’t prove a link between vaccination and side effects. The surveillance mechanism, not the study design, is the source of this restriction. Furthermore, the requirement for smartphone access to participate in v-safe excludes people who do not have access to such devices. Finally, while there are trends in adverse response differences between the Pfizer-BioNTech and Moderna mRNA vaccines, neither VAERS nor v-safe can clearly evaluate the vaccines’ safety differences.
Elizabeth Phillips, Vanderbilt University Medical Center USA, who was not engaged in the study, wrote in a linked comment: “For adverse events of special interest, it is reassuring that there were no unexpected signals other than myopericarditis and anaphylaxis, already known to be associated with mRNA vaccines.”
Source: 10.1016/S1473-3099(22)00054-8
Image Credit: Getty
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