On Monday, the Public Health Agency of Sweden recommended that people age 80 and older be given a second booster dose of the coronavirus vaccine, the fourth overall shot.
As the country lifted its pandemic restrictions, it also warned that the virus was spreading rapidly among people at risk of serious illness.
The country is among the few places to recommend the next dose as a booster, beyond the initial shots and a booster that experts say most adults should receive.
Anders Tegnell, the chief epidemiologist at Sweden’s Public Health Agency, said, “We believe that people 80 years and older will benefit from a second booster dose.”
Some scientists argue that it’s unrealistic to try to give everyone another shot, and the government should focus on providing booster doses to older adults—which the C.D.C. recommends.
People are particularly vulnerable because their immune systems are weakened, or they live in long-term care facilities like nursing homes.
Both vaccines in use in Sweden – developed by Moderna and by Pfizer and BioNTech – are usually administered in two initial doses a few weeks apart.
According to the Our World in Data project at the University of Oxford, seventy percent of Swedish residents have been fully vaccinated or have received the initial two doses.
Many countries recommend that people with weak immune systems get three shots instead of two for their initial vaccination. Booster shots will then be advised on the same basis as those who received the standard two-dose initial vaccination.
Recent studies have found that only an early vaccination, without a booster, remains strongly protective against serious illness and death in most people, including Omicron, even though its effectiveness against infection diminishes over time.
