Three reviews have found that vaccination continues to provide strong protection against severe disease and mortality for at least six months post-vaccination
The Health Information and Quality Authority (HIQA) has published the 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. The first update focused on healthcare workers, while the 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 similar high levels of protection against severe disease 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. Given this and the potential lower vaccine response for these populations, 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 protection are due to waning immunity, differences in exposure, increased transmissibility and or vaccine escape from new variants, or a mixture of all these factors," he said.
"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 protection possible," Dr O’Loughlin said.
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