Over a 20-year period, vaccines approved by the US Food and Drug Administration (FDA) were found to be remarkably safe in post-marketing surveillance studies, according to Israeli research published in the Annals of Internal Medicine.

The retrospective cohort study by physicians Noam Tau, Dafna Yahav and Daniel Shepshelovich, all affiliated with Tel Aviv University’s medical school, was the first to check the prevalence and clinical significance of emerging post-approval, vaccine-related safety issues.

“Vaccines are one of the greatest achievements in public health,” the authors state.

They examined the initial and subsequent labels of all 57 vaccines that were FDA-approved between January 1, 1996 and December 31, 2015. Fifty-three of these vaccines (93%) had initially been approved through a process of randomized controlled trials.

The Israeli doctors identified 58 post-approval, safety-related label modifications associated with 25 of the 57 vaccines There were 49 warnings and precautions, eight contraindications and one safety-related withdrawal from the market (RotaShield).

The most common safety issue (36%) that triggered a label modification was a tighter restriction on which populations should use it. The second most common modification (22%) was allergy warnings.

The most common source of safety data was post-marketing surveillance, accounting for 28 of the 58 label modifications.

“A large proportion of safety issues were identified through existing post-marketing surveillance programs and were of limited clinical significance,” the authors conclude.

“These findings confirm the robustness of the vaccine approval system and post-marketing surveillance.”