Immunity from Covid-19 lasts up to six months after infection – Hiqa

Immunity after Covid-19 infection can last up to six months, the State’s health watchdog has advised.

This is twice the 12-week period that had applied as guidance in Ireland up to now.

Post-infection guidance for close contacts should be extended to six months in line with the new evidence, according to the Health Information and Quality Authority (Hiqa).

The studies Hiqa examined were conducted prior to last December. Since then, new variants of Sars-CoV-2 have been found and the vaccine rollout has begun.

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As a result, it says the applicability of the findings to the new strains and vaccinated populations is unknown.

“We have advised Nphet presumptive immunity should be extended to six months post-infection. The risk of reinfection with Sars-CoV-2 is low and no evidence was found to suggest that immunity wanes over this period,” said Dr Máirín Ryan, Hiqa’s deputy chief executive and director of health technology assessment.

Infection

The review identified five studies reporting low rates of reinfection up to seven months following initial infection.

In relation to the long-term duration of immune responses, it found that, while there may be a waning of antibody responses over time, T- and B-cell responses persist for up to eight months post-infection.

On Monday evening, deputy chief medical officer Dr Ronan Glynn said the National Public Health Emergency Team (Nphet) had endorsed the recommendation to extended the recognised period of immunity, and the HSE was currently updating its recommendation to reflect the change.

The recommendation from Hiqa could have significant implications for policy in a number of pandemic-related areas. More people could be exempted from serial testing requirements and from the requirement for testing prior to hospital admission.

As a result, fewer healthcare workers would be unavailable due to being close contacts, if the recommendation is implemented.

However, Hiqa cautions that, given the uncertainty around new variants, any policy changes may not be applicable to exposure to “immune escape” new variants. It also says changes should be kept under review to take account of international evidence and surveillance data.

In addition, the studies that were reviewed largely involved the general population and healthcare workers, and Hiqa warns it is unclear if the findings are generalisable to the elderly, those with other condition and immunity issues.