People who have recovered from a Covid-19 infection must continue to follow all public health advice, including hygiene and physical distancing.

That is according to a new study by the Health Information and Quality Authority.

The study of the experience worldwide, found that after infection, immunity is sustained for at least two months and for some up to six months.

HIQA conducted this review of the potential for reinfection following a Covid-19 infection at the request of the National Public Health Emergency Team.

The study found that reinfection cases are rare events, and to date 14 patients worldwide have been infected twice.

Genetic evidence shows that the first and second infections were caused by different strains.

Dr Mairin Ryan, HIQA deputy CEO, said that the phenomenon of reinfection has significant policy implications.

"Infection prevention and control, isolation and contact tracing considerations are not likely to differ for cases of reinfection compared with the first infections," she said.

Dr Ryan said that all public health advice should apply to those who have recovered from Covid-19 as immunity from infection can not be assumed.

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Speaking on RTÉ's News at One, Dr Ryan said based on its research, it may not be possible for a Covid-19 vaccine to produce long-term immunity and a booster may be needed.

She said this is not that surprising as immunity does wane over time with a number of vaccines and boosters are required.

Dr Ryan said one element of the antibody response that is being noted - neutralising antibodies - are waning after a couple of months.

She said: "A lot of vaccines are designed to cause the body to produce neutralising antibodies... if they behave in the same way as what we're seeing with the natural infection, then it means that the immunity that's produced by the vaccine may wane over time."

She said it may not be possible therefore for the vaccine to produce long-term immunity and people may need booster doses.

Dr Ryan said people who have had the coronavirus and who show symptoms that are consistent with Covid-19, should continue to observe all the public health advice and contact their GP for a test as they "can't assume that immunity from re-infection is taking place".

She acknowledged that the documented cases of re-infection are rare, but as earlier tests were done on those who were very symptomatic and not those who were mildly symptomatic or asymptomatic, it is "very likely that there are substantially more cases of re-infection out there and more cases will be reported as we go forward".