Potential COVID-19 vaccine side effects are more common in actual infection

A recent study found that potential side effects from COVID-19 vaccines that many people use as an excuse not to get vaccinated pale in comparison to the severity of the same symptoms an unvaccinated person who becomes infected with the coronavirus may experience. 

The study, which was published in "The New England Journal of Medicine" on Aug. 25, used data from the largest health care organization in Israel to evaluate the safety of the Pfizer-BioNTech COVID-19 vaccine. 

"For each potential adverse event, in a population of persons with no previous diagnosis of that event, we individually matched vaccinated persons to unvaccinated persons according to sociodemographic and clinical variables," according to the study. 

A total of 2.4 million people were observed and the median age was 43. 

Pfizer vial

FILE - A nurse reaches for a vial of Pfizer-BioNTech COVID-19 vaccine at a pop-up vaccine clinic. (ROBYN BECK/AFP via Getty Images)

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The side effects researchers highlighted were lymphadenopathy, which is swelling of lymph nodes (78.4 events per 100,000 persons), shingles (15.8 events), appendicitis (5.0 events) and myocarditis — also known as heart inflammation (2.7 events). 

Each vaccinated participant had a follow-up checkup after 21 days following their first and second doses of the COVID-19 vaccine, according to the study. 

"A total of 42 days was deemed to be sufficient for identifying medium-term adverse events, without being so long as to dilute the incidence of short-term adverse events," researchers said. 

The study’s main findings were that people who were vaccinated against COVID-19 experienced normal to low severity in side effects whereas those who became infected with COVID-19 experienced far more adverse symptoms in addition to the side effects experienced with the COVID-19 vaccine. 

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For instance, people who were vaccinated experienced 2.7 events of heart inflammation out of 100,000 in comparison to 11.0 events of heart inflammation out of 100,000 for unvaccinated people who were infected with COVID-19. 

Researchers also noted those who were unvaccinated experienced higher cases of arrhythmia (166.1 events per 100,000 persons), acute kidney injury (125.4 events), pulmonary embolism (61.7 events), deep-vein thrombosis (43.0 events), myocardial infarction (25.1 events), pericarditis (10.9 events) and intracranial hemorrhage (7.6 events). 

"Moreover, infection with SARS-CoV-2 has many other adverse effects beyond those considered here, including the risk of transmission to family members and others," according to the study. 

Apart from the previous symptoms associated with COVID-19 highlighted in the Israel study, another study published on July 15 in the medical journal "The Lancet" found more than 200 symptoms affecting 10 organ systems for an extended period in people who were infected with the novel coronavirus. 

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While the U.S. Centers for Disease Control and Prevention said most people recover from COVID-19 after two weeks, the 3,762 respondents of "The Lancet" study took longer than 35 weeks on average to recover from the virus. 

Researchers said fatigue was the most common symptom, in some cases lasting up to six months. Cognitive dysfunction and post-exertional malaise — the worsening of symptoms following minor physical or mental exertion — were also among the most commonly observed symptoms. 

Eighty-eight percent of respondents reported a decline in cognitive dysfunction or memory issues. 

"Patients with Long COVID report prolonged, multisystem involvement and significant disability," study authors wrote. "By seven months, many patients have not yet recovered (mainly from systemic and neurological/cognitive symptoms), have not returned to previous levels of work, and continue to experience significant symptom burden." 

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Currently, several symptoms of COVID-19 identified in the study are not recognized by the CDC. Symptoms like "COVID toes" and "rheumatoid arthritis" aren’t listed on the agency’s website detailing the long-term effects of the novel coronavirus. 

More serious long-term complications appear to be less common but have been reported, such as lung function abnormalities, acute kidney injury, hair loss, smell and taste problems, sleep issues, difficulty with concentration, memory problems, depression, anxiety and changes in mood. 

The CDC said, "While most persons with COVID-19 recover and return to normal health, some patients can have symptoms that can last for weeks or even months after recovery from acute illness." 

In another study published in "The Lancet" on Sept. 1, those who are vaccinated against COVID-19 but still became infected with the virus — also known as a breakthrough case — were less likely to develop long-COVID-19 symptoms as opposed to those who are unvaccinated. 

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"We found that the odds of having symptoms for 28 days or more after post-vaccination infection were approximately halved by having two vaccine doses," researchers wrote in the study. "This result suggests that the risk of long COVID is reduced in individuals who have received double vaccination when additionally considering the already documented reduced risk of infection overall." 

In addition to being less likely to develop long-COVID, fully vaccinated individuals were also less likely to have more than five symptoms in the first week of illness and less likely to be hospitalized, compared to unvaccinated people, the researchers said. 

Overall, COVID-19 symptoms were more common in the unvaccinated participants across age groups. 

Meanwhile, the U.S. Food and Drug Administration’s scientific advisers are set to debate Pfizer's evidence arguing for a booster dose of their COVID-19 vaccine later this month. 

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What's ultimately recommended for an 80-year-old vaccinated back in December may be different than for a 35-year-old immunized in the spring — who likely would get a stronger immunity boost by waiting longer for another shot. 

If the FDA approves another dose, then advisers to the CDC will recommend who should get one. 

That's tricky because while real-world data shows the vaccines used in the U.S. remain strongly protective against severe disease and death, their ability to prevent milder infection is dropping. It's not clear how much of that is due to immunity waning or the extra-contagious delta variant — or the fact that delta struck just as much of the country dropped masks and other precautions. 

When to jump to boosters "becomes a judgment," said Dr. Jesse Goodman of Georgetown University, a former FDA vaccine chief. "And is that urgent or do we have time for the data to come in?" 

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Already the CDC is considering recommending the first boosters just for nursing home residents and older adults who’d be at highest risk of severe disease if their immunity wanes — and to front-line health workers. 

Some other countries already have begun offering boosters amid an ethical debate about whether rich countries should get a third dose before most people in poor countries get their first round. 

Pfizer and Moderna have filed FDA applications for booster doses but the government will decide on extra Johnson & Johnson doses later, once that company shares its booster data with the agency. 

The Associated Press, Austin Williams and Kelly Taylor Hayes contributed to this report. This story was reported out of Los Angeles.