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People who experience particular side effects after receiving a COVID-19 vaccine, such as swollen lymph nodes, may have been previously infected with the coronavirus, according to a new study published to the medRxiv prepress server. The study has not yet been peer-reviewed.
Common side effects such as fever, fatigue, muscle aches and joint pain were also more common among those who had previous infections.
An earlier COVID-19 infection, but not what is known as “long-term COVID-19,” was associated with an increased risk of swollen lymph nodes after receiving the vaccination, the study authors wrote. .
Researchers at three UK hospitals surveyed healthcare workers after the first dose of the Pfizer vaccine. Among the 974 health workers surveyed, 265 reported a positive COVID-19 test or antibodies before being vaccinated.
Women and young people were more likely to report more side effects, greater severity, and longer duration of symptoms, the authors wrote.
About 4% of those who had already recovered from COVID-19 experienced swollen lymph nodes after vaccination, compared with less than 1% of those who did not have a previous infection. In addition, 8% of those who had contracted COVID-19 reported fever as a side effect, compared with 2% of those who had never been infected.
Muscle pain and fatigue were also reported more frequently. About 30% of those who had already been infected reported muscle pain, compared with 15% who did not have a previous infection. About 29% who contracted COVID-19 reported fatigue, compared with 20% who did not contract the virus.
Injection site pain and gastrointestinal symptoms were almost the same in both groups.
Among the 265 health workers who had previous COVID-19 infections, 30 people reported symptoms of long-term COVID-19 that were ongoing months after they became ill. Long-term COVID-19 was not associated with more serious side effects from the vaccine.
In addition, the research team did not find a significant difference in the number or severity of side effects based on the chronology of when people became infected and when they received the vaccine.
“There are implications for public health in terms of vaccination hesitation, which is somewhat motivated by fear [adverse effects]”, wrote the authors of the study.
“These data may support vaccine – related education [adverse effects] and, through better understanding, they help combat vaccine vaccination, ”they added.
medRxiv: “Previous COVID-19 infection, but not long-term COVID, is associated with an increase in adverse events after BNT162b2 / Pfizer vaccination.”