New, more contagious subvariants of the Omicron variant of the SARS-CoV-2 coronavirus have been detected in Croatia, causing a considerable increase in the number of new COVID-19 cases this week, the Croatian Public Health Institute (HZJZ) warned on Friday.

In a situation where all epidemiological measures have been lifted, the virus is spreading faster, and the new subvariants BA.4 and BA.5 are more successful in avoiding the immunity acquired by vaccination or recovery, the HZJZ said.

On Friday, Croatia registered 612 new COVID-19 cases and four related deaths, compared to 206 new cases recorded on June 1.

The subvariants BA.4 and BA.5 have been found in 15 percent of the samples that Croatia has sent to a European laboratory for sequencing.

The HZJZ noted that, despite the greater virulence of the new subvariants, vaccinated people are still pretty well protected against more serious forms of the disease and hospitalisation.

People who have recovered from COVID-19 are recommended to get vaccinated at least three months after the recovery because the protection acquired by recovery subsides over time.

The director of Zagreb’s Fran Mihaljevic Hospital for Infectious Diseases, Alemka Markotic, said that the situation was being closely monitored and that she could not rule out the possibility that the current increase in case numbers would be called a new wave of the epidemic.

“The spread of the subvariants BA.4 and BA.5 makes it possible for people who have been vaccinated or who have recovered to be infected, but these are mostly mild clinical forms that pass in a day or two. It is important that chronic patients continue to practise epidemiological measures and protection, so we invite them again to get vaccinated,” Markotic told the Croatian state news agency Hina.

She noted that the two new subvariants were likely to soon become dominant in Europe, and added that new Omicron-specific vaccines are yet to be registered in Europe or the United States.