The risk of a person who had Covid-19 getting reinfected is low for more than 12 months after the initial infection, according to latest assessment by the State’s health watchdog.
However, there is some evidence that the duration and/or the extent of protective immunity following infection may be lower in older people, as well as patients with chronic kidney disease and immunocompromising conditions, the Health Information and Quality Authority (Hiqa) found.
Despite the evidence of longer-last immunity post-infection, Hiqa has decided not to change its advice that the period of presumptive immunity is nine months.
This follows a meeting of its expert advisory group, at which concerns were expressed about the applicability of the study data and the ramifications of such a change.
Because the studies considered were observational and carried out during periods of stringent public health measures and less transmissible variants than the current Delta variant, they may have “limited generalisability” to the current context, the group advised.
"Given the uncertainty regarding current epidemiological trends in Ireland, there are concerns regarding the potential negative impact of extending the period of protective immunity post-infection.
“The additional protection provided by vaccination to those previously infected should be clearly communicated to the public,” it also advised. “In addition, there should be clear messaging that natural immunity does not provide absolute protection from reinfection.”
Members expressed the view that despite the “encouraging” evidence about low reinfection risk, extending the duration of presumed protective immunity from nine months “may raise the risk of reinfection”.
The new advice is the eight of recommendations from Hiqa on the issue and looked at 65 studies that investigated the risk of Covid-19 reinfection. But only 12 of the studies were considered of high enough quality to be use in framing the advice.
Healthcare workers are disproportionately affected by reinfections, data indicates, so the most significant impact of any change to the presumed period of immunity would be felt in this sector.
Hiqa says staff at the tail-end of this period may only develop mild symptoms or not at all but they can still transmit the virus to colleagues and patients.
“This potential for the spread of virus amongst [healthcare workers] with waning immunity, and to their patients, should be to the fore of any decision to extend the duration of presumed protective immunity.”