Your menstrual cycle may be slightly disrupted after a flu vaccine

Embargoed until: Publicly released: 2025-04-30 01:00

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The influenza vaccine is associated with small, temporary changes in the menstrual cycle, regardless of whether you get it alongside a COVID-19 vaccine, according to an international study. The researchers collected menstrual cycle data from 1,501 women who either received a flu shot or both a flu and COVID-19 vaccine at the same time. They say receiving a vaccine was linked with a small change in menstrual cycle length - less than a day on average - with no meaningful difference between the two groups. They say menstrual cycle changes occurred for women who were vaccinated during the first half of their menstrual cycle, but not for women vaccinated in the second half.

Media release

From: JAMA

Menstrual Cycle Length Changes Following Vaccination Against Influenza Alone or With COVID-19

About The Study: In this cohort study of individuals with regular menstrual cycles, influenza vaccine given alone or in combination with a COVID-19 vaccine was associated with a small but temporary change in menstrual cycle length. These findings may help clinicians confirm the utility of vaccination for patients with concerns about menstrual adverse effects of vaccination.

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Research JAMA, Web page The URL will go live after the embargo ends

Journal/
conference: JAMA Network Open

Research:Paper

Organisation/s: Oregon Health & Science University, USA

Funder: This study was supported by grant NICHD089957 from the US National Institute of Child Health and Human Development (principal investigator, Dr Edelman).

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