Unvaccinated people with Covid-19 pose ‘greatest risk’ of transmission - Niac

Unvaccinated people with Covid-19 pose the “greatest risk” of transmission in the health system, the State’s expert group on immunisation has warned.

However, vaccinated healthcare workers with breakthrough infections can "unwittingly" cause outbreaks in hospitals and care homes, affecting both staff and patients, the National Immunisation Advisory Committee says.

In its recommendation for administering booster vaccine shots to healthcare workers, Niac warns these will not immediately contribute to the management of outbreaks, or take the place of public health and other measures.

Healthcare workers who have completed a course of any of the four authorised vaccines are now recommended to receive a booster dose of mRNA vaccine (Pfizer or Moderna), with frontline workers being prioritised. Niac is recommending a full dose of Pfizer or a half-dose of Moderna be given at least six months after completion of initial vaccination, though a minimum interval of five months can be used "for operational reasons".

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Healthcare workers who have been infected after initial vaccination should defer a booster for at least six months after infection.

Boosters

On Monday night, Minister for Health Stephen Donnelly approved Niac's recommendation and said the administration of booster shots to healthcare workers would start this weekend.

In the recommendation, Niac says that although Covid-19 antibody levels wane over time after vaccination, effectiveness against severe disease and death is “generally sustained”. However, protection against infection “and mild disease” declines.

Healthcare workers accounted for under 5 per cent of cases in the second half of October, according to Niac. Of the 60 per cent of cases where the likely source of transmission was known, less than 2 per cent were acquired in a healthcare setting.

While the “main aim” of the vaccination programme is to prevent severe disease and death, “decreasing the incidence of HCW infection will reduce the risk of transmission and help protect vulnerable patients”.

Boosters for healthcare workers will reduce the incidence of breakthrough infection, provide additional protection for patients “and may also help support continuity of healthcare services,” Niac says.

“Booster doses of mRNA vaccines have not shown any unexpected short term safety concerns. The risk of myocarditis or other rare adverse reactions following an mRNA booster dose has yet to be characterised and will be closely monitored.”

Niac says it “continues to examine” new evidence on the durability of protection provided by vaccines in other groups, including under-60s with comorbidities.