Does it matter if one skips the second shot?

From a practical standpoint, missing the second shot could create problems down the road if workplaces, college campuses, airlines and border patrol agents require proof of full vaccination.

But many people aren’t getting the message that the second dose matters. More than five million people, or nearly 8 percent of those who got a first shot of the Pfizer or Moderna vaccines, have missed their second doses, according to the most recent data from the Centers for Disease Control and Prevention. The reasons people are missing their second shots vary. Some people say they are worried about side effects, which have widely been reported to be worse after the second dose. Others say second shot appointments have been canceled, and it’s been hard to reschedule. But new research also shows that many people are just confused and wrongly think one shot is enough.

Researchers from Cornell University and Boston Children’s Hospital surveyed a representative sample of more than 1,000 Americans in February, and found that 20 percent believed they were strongly protected after just one dose of a two-dose vaccine. (Another 36 percent said they weren’t sure how protected they were.) And among those respondents who had already received at least one shot, 15 percent didn’t remember being told to come back for a second dose. About half didn’t remember anyone telling them that protection was strongest after the second dose, according to the report, published in The New England Journal of Medicine. “Our survey exposed the fact that there is still a lot of confusion about the timing of protection when it comes to getting vaccinated,” said John Brownstein, an epidemiologist and chief innovation officer at Boston Children’s Hospital and a co-author on the research.

Adding to the confusion is the fact that some countries are delaying second doses so they can get more people vaccinated more quickly or because they have limited supply of vaccine. Both the Pfizer and Moderna vaccines are what’s known as mRNA vaccines and require two shots, ideally spaced three or four weeks apart. But in some countries, including Britain and Canada, second shots have been delayed by as long as three or four months. While that strategy has worked for countries facing distribution problems or vaccine shortages, Dr. Anthony S. Fauci, the director of the National Institute of Allergy and Infectious Diseases, has repeatedly resisted calls to adopt a one-dose strategy in the United States. The C.D.C. recently reported that a study of health care and emergency workers at high risk for exposure to the coronavirus found a single dose of Pfizer’s or Moderna’s COVID-19 vaccine was 80 percent effective at preventing COVID-19. After the second dose, the vaccines were about 90 percent effective.

But vaccine experts say those numbers can mislead people into thinking there’s very little benefit from the second dose, and fail to capture some of the important changes that happen inside the body after a person is fully vaccinated with both doses. “The second dose of mRNA vaccines induces a level of virus neutralising antibodies about 10-fold greater than the first dose,” said Dr. Paul Offit, a professor at the University of Pennsylvania and a member of the Food and Drug Administration’s vaccine advisory panel. “Also, the second dose induces cellular immunity, which predicts not only longer protection, but better protection against variant strains.”

Tara Parker-Pope is a journalist with NYT©2021

The New York Times