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Vaccinated People Also Spread the Delta Variant, Yearlong Study Shows

  • Study found similar peak viral load with or without shots
  • Immunized household contacts have a 25% chance of infection
A Pharmacy Administers Third Doses Of Covid-19 Vaccines
Photographer: Emily Elconin/Bloomberg

People inoculated against Covid-19 are just as likely to spread the delta variant of the virus to contacts in their household as those who haven’t had shots, according to new research.

In a yearlong study of 621 people in the U.K. with mild Covid-19, scientists found that their peak viral load was similar regardless of vaccination status, according to a paper published Thursday in The Lancet Infectious Diseases medical journal. The analysis also found that 25% of vaccinated household contacts still contracted the disease from an index case, while 38% of those who hadn’t had shots became infected.