The researchers surveyed over 900 healthcare workers in three different hospitals as part of their longitudinal observational study. They found that 265 of the participants were infected with the coronavirus prior to getting their first Pfizer vaccine. Thirty of those were experiencing what is known as "Long-COVID."
Long-COVID, or long haulers, are people who continue to experience at least some coronavirus symptoms four weeks after first observing the signs and symptoms of the virus. Some of the most common Long-COVID symptoms include coughing, breathlessness, fatigue and "brain fog" – problems with concentration and memory.
The researchers noted that people with Long-COVID were not more likely to experience adverse reactions than the general population. But they also pointed out that too few Long-COVID sufferers were included in the study to create any definitive conclusions regarding them. (Related: Australian doctor "shocked" by adverse effects of Pfizer coronavirus vaccine's second jab.)
People with history of COVID-19 more likely to experience adverse vaccine-related events
The study, published in the pre-print server MedRxiv, found that healthcare workers with a prior COVID-19 infection – excluding people with Long-COVID who were still experiencing coronavirus symptoms – reported at least one adverse event the researchers described as "moderate-to-severe."
Seventy-five percent of the adverse events were reported within 24 hours after receiving the first dose of the Pfizer vaccine, with the rest being reported within 48 hours.
Women and younger people were more likely to experience adverse events, and women were also more likely to experience the side effects for longer periods.
The researchers were able to find five adverse events that were significantly correlated with previous COVID-19 infection: fever, fatigue, muscle pain, joint pain and swelling of the lymph nodes.
Of these five symptoms, the U.S. Centers for Disease Control and Prevention (CDC) only recognizes swelling of the lymph nodes to be a "serious adverse event." The CDC has reported that at least 38,000 participants in Pfizer-BioNTech's Phase III trial experienced swelling of the lymph nodes. The rate of swollen lymph nodes was higher in the vaccine group than in the placebo group.
Four percent of the U.K. study participants with a prior COVID-19 infection reported swollen lymph nodes, compared to less than one percent in those with no history of coronavirus.
The vaccinated healthcare workers also experienced other symptoms, such as redness and swelling around the vaccine injection site and gastrointestinal concerns. But these adverse events were not associated with a history of COVID-19.
For the group that had prior coronavirus infections, pain was the most common adverse event followed by fatigue, headaches, mylagia (muscle pain) and anthralgia (joint pain).
The study has demonstrated that the coronavirus vaccines present an increased risk of adverse events in those with prior COVID-19 infection. The authors are suggesting that further consideration is needed before people with a history of coronavirus take the second vaccine dose, particularly given reports of more severe adverse events following the completion of vaccination.
"Our findings add to other reports supporting wider understanding of [adverse events] following COVID-19 vaccination," wrote the authors, who hope that their findings "may help inform those with previous COVID-19, including Long-COVID, of increased susceptibility" to adverse events.
Learn more about the adverse events caused by the different coronavirus vaccines such as Pfizer by reading the latest articles at Vaccines.news.
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