Israel started injecting a fourth dose of the COVID-19 vaccine Friday (Dec. 31) amid a wave of new cases driven by the Omicron variant.
The country is administering the extra dose to people with weakened immune systems, as well as elderly residents and employees in care homes.
Israel—which had the highest percentage of its 9.3 million residents fully vaccinated than any other country in late 2020 and early this year—is one of the first nations to allow the fourth dose.