Sweden recommends fourth vaccine shots for people 80 and older.
Sweden’s public health agency recommended on Monday that people 80 and over receive a second booster dose of coronavirus vaccine, which would be a fourth overall shot. It also warned, as the country removes its pandemic restrictions, that the virus is spreading increasingly among people who are at elevated risk of severe illness.
The country is among the few places to recommend a fourth dose as a booster, beyond the initial shots and one booster that experts say most adults should receive.
Data published by the U.S. Centers for Disease Control and Prevention last week suggested that the added protection from booster shots tends to diminish significantly after about four months, raising the possibility that people who would be at high risk of serious complications or death if they contracted Covid-19 may need another dose.
Before Omicron emerged, officials and scientists debated whether boosters were necessary or advisable for people of various ages as a wide swath of nations authorized them anyway. But there was a broad shift in that thinking as Omicron, which evades immune defenses better than previous variants, swept the world, leading to more support for boosters.
“We believe that people who are 80 years and older will benefit” from a second booster dose, said Anders Tegnell, chief epidemiologist at Sweden’s public health agency.
Some scientists argue that trying to give everyone another shot every few months is unrealistic, and that booster efforts should be focused instead on older adults — who appear to get the most benefit from boosters, according to C.D.C. data — and on people who are especially vulnerable because they have weakened immune systems or live in long-term care facilities like nursing homes.
Both vaccines in use in Sweden — those developed by Moderna and by Pfizer and BioNTech — are usually administered in two initial doses a few weeks apart. Seventy-three percent of Swedish residents are considered fully vaccinated, or having received the initial two doses, according to the Our World in Data project at the University of Oxford.
Many countries recommend that people with compromised immune systems receive three shots for their initial vaccination, instead of two. Booster shots would then be advised for those people on the same basis as for people who received the standard two-dose initial vaccination.
Recent studies have found that an initial vaccination alone, without boosters, remains strongly protective against severe illness and death in most people, including against Omicron, even though its effectiveness against infection declines over time.
Sweden has eased or lifted most of its pandemic restrictions this month, including work-from-home requirements and limits on the size of gatherings. Like many countries, Sweden saw a huge surge in daily reports of new cases in January, propelled by the Omicron variant; more recently the figure has been falling, though it remains high.
Along with all people 80 or older, Sweden is recommending that others who live in nursing homes or who receive assisted-living services at home should also receive a second booster dose, at least four months after their first one, the country’s health agency said.