HIQA publishes advice on Covid-19 reinfection and immunity

HIQA has published advice on the potential for reinfection and the duration of immunity following an infection with SARS-CoV-2.

The advice has been submitted to the national public health emergency team (NPHET) and is  accompanied by a supporting evidence synthesis report.

In this update, HIQA has reviewed new evidence relating to the possibility of reinfection following recovery from SARS-CoV-2, as well as studies with longer follow-up looking at the duration of immunity following infection.

 “New evidence has demonstrated that reinfection can occur following recovery from SARS-CoV-2 infection,” said Dr Máirín Ryan, HIQA’s Deputy CEO and Director of Health Technology Assessment.

“Worldwide, at least fourteen patients have been infected twice by SARS-CoV-2; these reinfections were confirmed by genetic evidence that showed the first and second infections were caused by different viral strains. It is important to remember, however, that these are rare events.

 “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 infection.

“Therefore, all public health advice, including hygiene and physical distancing, should apply to those who have recovered from a SARS-CoV-2 infection as immunity from reinfection cannot be assumed.”

The evidence summary also reviewed the current evidence on the maximum duration of immunity following infection. Dr Ryan said: “Evidence from 22 studies suggests that IgG antibody levels (the most common antibody in the blood) are sustained for at least two months after infection, and for some even up to six months. The levels of neutralising antibodies (that can neutralise viruses like SARS-CoV-2), decline over time, especially in the later stages of follow-up. While this doesn’t offer a full picture of the body’s response to SARS-CoV-2, these data have implications for vaccine development, antibody testing and immunotherapy going forward.”