The Health Information and Quality Authority (HIQA) has today published three reviews on the duration of immunity following COVID-19 vaccination to inform the work of the National Immunisation Advisory Committee (NIAC).



HIQA reviewed international evidence in order to assess the duration of protective immunity following COVID-19 vaccination in the general population and in specific subgroups. The initial review examined the duration of protective immunity following COVID-19 vaccination in all populations aged 12 years and older. This was then updated with a focus on healthcare workers, with a second update focused on individuals with underlying conditions.



The reviews identified over 50 studies. While the risk of breakthrough infection increased over time, overall the evidence suggests that COVID-19 vaccination continues to provide strong protection against severe disease and mortality for at least six months post-vaccination. However, some studies suggest that there is waning protection particularly for older adults and in those with immunocompromising conditions. Studies that looked specifically at healthcare workers showed high levels of protection against severe disease, similar to that seen in the general population.



Dr Mark O’Loughlin, a Public Health Fellow in HIQA, said: “Despite the good protection afforded by vaccination, national and international data indicate a higher risk of severe disease outcomes in older individuals and in those with underlying conditions. As vaccine response is already potentially lower in these populations to begin with, any additional reduction in protection would be of concern.”



Public health measures, infection prevalence and vaccination rollout have varied across countries and over time. Additionally, new variants of concern have emerged. It is difficult to determine if reductions in vaccine protection are due to waning immunity, different levels of exposure, the impact of variants of concern, or a mixture of all these factors.     



Dr O’Loughlin continued: “There is some uncertainty regarding protection after six months, especially in relation to new variants of concern and changing public health measures. We would encourage anyone who has been offered a booster dose, to avail of it and give themselves the best possible protection.”



You can find these documents from the link at the top of the page.

Ends.

Further information:

Marty Whelan, Head of Communications & Stakeholder Engagement

01 814 7480/085 805 5202, mwhelan@hiqa.ie



Notes to Editor:

• HIQA has today published the following three reviews to inform the work of the National Immunisation Advisory Committee (NIAC):
  • Duration of protective immunity following COVID-19 vaccination
  • Duration of protective immunity following COVID-19 vaccination of healthcare workers
  • Duration of protective immunity following COVID-19 vaccination of individuals with underlying conditions
• The duration of protective immunity from COVID-19 following vaccination is an important consideration for Ireland’s vaccination strategy, particularly for groups who may be at a higher risk of exposure (such as healthcare workers), those who have a less than optimal response to vaccination, or for whom there is evidence that immunity may wane over time.
• These three reviews were conducted in sequence, with the second and third reports based on updated literature reviews. The three reviews did not examine the impact of booster doses.
• As of December 2021, following conditional marketing authorisation from the European Medicines Agency, four COVID-19 vaccines are licensed and distributed for use in Ireland. These are ChAdOx1 (AstraZeneca), Ad26.COV2.S (Janssen), mRNA-1273 (Moderna) and BNT162b2 (Pfizer/BioNTech).  
• HIQA conducts evidence synthesis to inform national strategic decision-making. These evidence syntheses are conducted at the request of the National Public Health Emergency Team (NPHET) and related groups tasked with the national COVID-19 response.
• 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.