As efforts to limit the spread of COVID-19 continue around the world, Sweden and South Korea have encouraged high-risk individuals to receive a fourth dose of the vaccine.

The Centers for Disease Control and Prevention (CDC) published a report this month with findings that the booster shot's efficacy lasts only around four months. This implies that immunocompromised and older individuals would still be at a higher risk than others after a third dose of the vaccine, indicating that a fourth dose would provide increased immunity.

The agency still urges all people above the age of 12 to get boosted five months after getting the first two doses of the Pfizer or Moderna mRNA vaccines.

South Korean health minister Kwon Deok-cheol said in a COVID response discussion that the country intends “to provide fourth shots to those who live in nursing homes and care facilities and others with declined immunization, in light of a recent increase of infections among people aged 60 or older."

Chief epidemiologist of the Swedish public health agency Anders Tegnell said that “people who are 80 years and older will benefit” from an extra booster shot. The country's health officials announced last month, however, that it will not advise the COVID-19 vaccine for children who are between the ages of 5 and 11 as they don’t see a “clear benefit with vaccinating” children.

According to the scientific online publication Our World In Data, nearly 73% of Sweden’s population is fully vaccinated. The Wall Street Journal reports that around 82% of South Korea's population is vaccinated.