An expert in communicable diseases said on Tuesday that while Covid-19 vaccines do not provide complete protection against infection, they significantly reduce the risks of hospitalisation, severe illness and death.

Albert Au, head of the Centre for Health Protection's communicable disease branch, made the comment on an RTHK radio programme after health officials reported on Monday that an unvaccinated toddler was in a critical condition while a teenager who was vaccinated and suffering from underlying illness was in a serious condition.

Both contracted Covid in recent days.

Au said each individual's response to a Covid infection varies based on health status and pre-existing conditions and that a notable rise in outbreaks has been detected in schools and nursing homes.

"Looking at adult cases, we have substantial scientific evidence demonstrating the effectiveness of vaccines," he said.

"We have recorded more severe cases recently and over the past four weeks. We recorded 75 severe adult Covid cases, including 26 deaths, which is an increase from the prior four weeks where there were only 17 severe adult cases, including three deaths.

"The epidemiological characteristics of the recent severe adult cases are similar to previous ones, with 85 percent affecting those aged 65 and over.

"Notably, about 64 percent of these cases are in nursing homes.

"It’s significant that around 95 percent of these adult severe cases had pre-existing conditions, and over 90 percent had not received a booster in the past six months."

Au said the level of Covid infections has risen significantly since mid-March, surpassing levels recorded in August, although it was still lower than the peaks in May 2023 and March 2024.