IRELAND’S HEALTH WATCHDOG Hiqa has submitted advice to NPHET that indicates people can become reinfected with the novel coronavirus SARS-CoV-2, though it is “rarely documented”.

Although we don’t know how long immunity lasts, the studies cited by Hiqa indicate that antibodies that respond to Covid-19 last between two to six months. 

It said that if natural immunity is short-lived, it would have “major policy implications relating to restriction of movements, convalescent plasma donation and vaccine
development”, and may require ”vaccine booster doses”.

“Current understanding of the immune response to SARS-CoV-2 is limited,” it emphasised.

The Health Information and Quality Authority (Hiqa) has today published the 12 pages of advice it submitted to the National Public Health Emergency Team (NPHET) on this issue.

Dr Máirín Ryan, Hiqa’s Deputy CEO and Director of Health Technology Assessment, said that new evidence has demonstrated that reinfection can occur after recovery from SARS-CoV-2.

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.

Dr Ryan continued: “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.

Dr Ryan 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 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.

Hiqa previously published evidence summaries on many aspects of the immune response following SARS-CoV-2 infection.

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.

You can read the Hiqa report, and Hiqa’s advice to NPHET, here.