One in five 'have systemic reaction' to Pfizer COVID-19 vaccine

But researchers tracking side effects during the UK rollout say the strong reactions reflect a robust immune response

More than 20% of people who receive Pfizer’s COVID-19 vaccine experience systemic side effects like fatigue or chills, according to self-reported real-world data.

Reports from tens of thousands of British recipients, mostly health workers, add to early anecdotal evidence that reaction to the mRNA vaccine’s second dose is more debilitating than to the first dose.

Among 40,000 total doses, 14% of recipients reported systemic side effects after the first dose, compared with 22% after the second dose, although no serious reactions