Covid: Vaccines and local incidence had significant impact on nursing home outbreaks - report

The rollout of the Covid-19 vaccine reduced the probability of an outbreak occurring in a nursing home during the third wave
Covid: Vaccines and local incidence had significant impact on nursing home outbreaks - report

Muireann Duffy

The rollout of Covid-19 vaccines reduced the probability of outbreaks in nursing homes and lessened their extent when they did occur, according to an updated report.

A review of data by the Health Information and Quality Association (Hiqa) and Health Protection Surveillance Centre (HPSC) found there were almost 600 suspected or confirmed outbreaks of Covid-19 in nursing homes between February 2020 and May 2021, with more outbreaks noted in the third wave than in the first two waves combined.

Of the 592 total, 375 were confirmed outbreaks involving residents, impacting 293 nursing homes around the country.

The updated review added data from the third wave to research conducted earlier in the pandemic, most notably reflecting the impact of the vaccine rollout.

Overall, people over 85, who represent 2 per cent of the total population, accounted for 9 per cent of Covid cases during the first wave, reducing to 2 per cent in both the second and third waves. People in this cohort accounted for between 12-14 per cent of hospitalised cases across all three waves and between 40-44 per cent of Covid-related deaths.

The review notes that the first wave of infections lasted 154 days, during which time over 600,000 PCR tests were conducted, while the second and third waves lasted 112 days and 171 days respecitevly, when 1.25 million and 3.5 million PCR tests were carried out.

The review found many of the risk factors for an outbreak occurring in a nursing home were the same as earlier in the pandemic, namely; an increased incidence of the virus in the local community, a higher number of nursing homes within close proximity of one another, and a higher number of beds within the nursing home.

Factors associated with a nursing home having a reduced probability of an outbreak included higher vaccination rates among residents, the nursing home having previously experienced an outbreak, and having an increasing population density around the home.

The report noted that rural areas and other cities around the country had a lower risk of outbreak compared to Dublin city, however, the risk in these areas grew substantially during the second and third waves.


Comparing a HSE-run nursing home with 73 beds, for which the probability of an outbreak occuring was 0.018 during the first wave, to a nursing home with just 30 beds, the 30-bed home was found to have been approximately 49 per cent less likely to experience an outbreak.

Illustrating the protective impact of vaccination, which began in nursing homes at the end of December 2020, during the third wave, a private 51-bed nursing home was found to have reduced their probabilty of experiencing an outbreak from 0.034 prior to vaccination to 0.001 after residents received their second dose.

Assessing factors which had an impact on the extent of an outbreak in a nursing home, the report notes the number of beds again increased the liklihood of outbreak being more substantial.

However, data from the third wave differed from the earlier two waves in regards to the impact local incidence had on the extent of outbreaks in nursing homes.

Regarding the third wave, the report says: "The direction of effect is that an increase in local incidence is associated with a lower extent of outbreak," perhaps due to visiting restrictions being implemented when cases in the community were rising.

The extent of outbreaks was also found to have reduced significantly from the first to the second wave.

Overall, the report found the probability of an outbreak occuring in a nursing home was "significantly associated with community incidence", the extent of outbreaks decreased in subsequent outbreaks, and the type of nursing home (public or private) did not impact the probability of occurance or extent.

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