The Health Information and Quality Authority (HIQA) has advised that the current public health policy which assumes a period of protective immunity of nine months post-infection with Covid-19 should not be changed.

HIQA has published its advice to the National Public Health Emergency Team (NPHET) on the duration of immunity following Covid-19 infection.

It reviewed 65 large observational studies involving over 1.4 million previously infected individuals, including 10 studies with over 12 months' maximum follow-up.

It found that the risk of Covid-19 re-infection was low within the timeframe of these studies. There was also evidence to suggest that vaccination provides additional protection to those previously infected with Covid-19.

HIQA's Deputy Director of Health Technology Assessment, Michelle O'Neill, said that even if people have been previously infected with Covid-19, it is possible that they can get infected again and spread the virus to others.

"We recommend that you continue to follow to public health guidance, and get vaccinated even if you have already recovered from Covid-19, as the vaccine will provide you with an additional layer of protection."

HIQA said that based on the evidence to date, re-infection with Covid-19 is still an uncommon occurrence, but it is more likely for certain groups, such as healthcare workers due to their increased risk of exposure.

HIQA is now looking at the latest evidence on how long immunity lasts after primary vaccination. That report is not expected until later in December.