HIQA advise NPHET to extend the period of presumptive immunity from six to nine months post-infection
The Health Information and Quality Authority (HIQA) has today published its advice to the National Public Health Emergency Team (NPHET) on the duration of immunity (and protection from reinfection) following SARS-CoV-2 infection.
This advice was informed by a review of international evidence including 19 large cohort studies of reinfection involving over 640,000 previously infected individuals. It was also informed by 13 studies on immune memory response along with expert opinion, from the COVID-19 Expert Advisory Group.
Dr Máirín Ryan, HIQA’s Deputy CEO and Director of Health Technology Assessment, said: “We have advised NPHET that the period of presumptive immunity should be extended from six to nine months post-infection. Across all the studies we examined, the risk of SARS-CoV-2 reinfection was consistently low, with no increase in infection risk over time. In addition, studies suggests that most people develop immune memory after a SARS-CoV-2 infection that lasts for at least nine months.”
Dr Ryan continued: “Increasing the period of presumptive immunity from six to nine months has widespread positive implications for people. For example, a person who has COVID-19 in the last nine months would be exempt from serial testing. A change would also increase the number of under-50s who only need one dose of a COVID-19 vaccine to be considered fully vaccinated. It would also have implications for the implementation and roll-out of the proposed ‘green certificates’. It will be important that any policy changes and the evidence behind them are clearly communicated and consistently applied.”
The potential impact of new variants on natural immunity is evolving rapidly and needs to be kept under review. Future changes in policy should be informed by the latest international evidence and national surveillance data.
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Notes to Editor:
- HIQA has today published or updated the following documents to inform NPHET’s response to COVID-19:
- Advice to the National Public Health Emergency Team: Duration of immunity (and protection from reinfection) following SARS-CoV-2 infection
- Evidence summary: Duration of immunity (and protection from reinfection) following SARS-CoV-2 infection.
- This is the seventh review HIQA has completed on the topic of immunity and reinfection.
- NPHET asked HIQA to provide advice on the following research question:
- “How long does protective immunity (that is, prevention of RT-PCR confirmed reinfection) last in individuals who were previously infected with SARS-CoV-2 and subsequently recovered?”
- “What is the duration of immune memory responses (T-cell and B-cell memory and or their components’ responses) following SARS-CoV-2 infection?”
- This evidence summary consists of two systematic reviews. The first investigated the risk of SARS-CoV-2 reinfection over time. It identified nineteen large cohort studies involving over 640,000 previously infected individuals, including six studies with over ten months follow-up. The second review identified thirteen studies that investigated immune memory responses at ≥6 months post-infection.
- Public health guidance has been updated to reflect an increase in the duration of presumptive immunity to nine months. Updated guidance can be found here.
- HIQA provides evidence-based advice to NPHET to inform public health policy, advice and practice in the context of COVID-19. HIQA’s advice is informed by research evidence developed by HIQA’s COVID-19 Evidence Synthesis Team.
- This advice to NPHET is developed with expert input from HIQA’s COVID-19 Expert Advisory Group. The COVID-19 Expert Advisory Group, chaired by Dr Máirín Ryan, is a multidisciplinary group, comprising nominated representatives from the relevant public health and clinical specialties, methodology experts, and public representation.
- The topics HIQA researches are outlined and prioritised by NPHET to ensure rapid access to the best available evidence relevant to the SARS-CoV-2 outbreak.