A Hamilton-based infectious diseases physician says the rising number of “breakthrough” COVID-19 cases can be attributed to the Omicron variant.

According to the Centers for Disease Control and Prevention, a breakthrough case occurs when a fully vaccinated person gets infected with COVID-19. People with vaccine breakthrough infections are able to spread the virus to others.

“This is the Omicron piece,” said Dr. Zain Chagla in an interview on Morning Live. “There are going to be more COVID cases among vaccinated individuals given that there is some immune escape to this variant.”

Ontario reported 2,421 new COVID-19 cases Thursday. Health Minister Christine Elliott said 1,530 of the cases are in fully vaccinated people and 891 of the infected people are not fully vaccinated or have an unknown vaccination status.

Chagla said the spike in breakthrough cases should not discourage people from getting the vaccine or booster shot.

“The vaccines will protect people from ending up in hospital,” he said.

Chagla pointed to data from South Africa that suggests the risk of hospitalization is lowered by 70 to 80 per cent in fully vaccinated individuals.

He noted that elderly people and individuals with underlying medical conditions primarily make up the high number of breakthrough cases.

In order to reduce the number of fully vaccinated people testing positive for COVID-19, Chagla said eligible individuals need to get their booster shot and continue following public health measures.