The United States has already delivered more than 4 million doses of COVID-19 vaccines for children under 5 years old to sites that will administer the shots, a Department of Health and Human Services (HHS) spokesperson said on Thursday.

People infected with the earliest version of the Omicron variant of the coronavirus, first identified in South Africa in November, may be vulnerable to reinfection with later versions of Omicron even if they have been vaccinated and boosted, new findings suggest.

People who were infected with an earlier version of the coronavirus and received three doses of an mRNA vaccine – such as the Pfizer/BioNTech shot – appear to be best protected against symptomatic infection by the Omicron variant, according to a large study. Additionally, COVID-19-related neurological symptoms – such as memory and concentration issues – can last half a year or more in some patients, according to a small study.

COVID-19 vaccination during pregnancy appears to lower newborns’ risk of coronavirus infection, according to a study conducted in Norway. Additionally, the risk of developing long COVID after infection with the coronavirus is lower for vaccinated people than for the unvaccinated, but not by much, according to a large study from the U.S. Department of Veterans Affairs.