BOSTON (CBS) –  There are certain side effects from the COVID-19 vaccine that may indicate a person was at one time infected with the coronavirus, according to a new study.

The study, which has not yet been peer-reviewed, surveyed almost 1,000 health care workers in the U.K. after they received their first Pfizer vaccine.

After vaccination, about four-percent of those previously infected with the coronavirus developed swollen lymph nodes compared to only one-percent of people without known previous infection.

Those previously infected were also more likely to report fever, muscle pain, and fatigue. Pain at the injection site and GI symptoms were about the same in both groups. And the interval between the time of infection and time of vaccination did not appear to be a factor.

But as a reminder, if you’ve had COVID-19 in the past, you still need to get vaccinated. And even though you may develop side effects, those side effects tend to be mild to moderate and last only 24-48 hours.

Dr. Mallika Marshall