Clarification sought on boosters for Janssen Covid-19 vaccine recipients

Studies have show that effectiveness of single dose product fell sharply after eight months

Minister for Health Stephen Donnelly has asked officials to clarify how soon people who got the Janssen Covid-19 vaccine should receive a booster dose.

A new recommendation will see some people who were administered the one-shot vaccine (also known as Johnson&Johnson) given a booster after three months.

But the recommendation from the National Immunisation Advisory Committee (Niac) applies to people in the three groups newly included in the booster programme – long-term care residents, people aged 16-59 with underlying conditions and anyone aged from 50-59 years.

No recommendation has been issued for the rest of the 236,000 people who were administered the Janssen vaccine, in spite of numerous international studies pointing to its effectiveness rapidly declining over time.


In one recent study of US veterans, the effectiveness of the vaccine against infection dropped from 86.4 per cent to 13.1 per cent over eight months, the biggest fall for any of the authorised vaccines. Protection against death was higher for Janssen, at 52.5 per cent after eight months.

In its recommendation, Niac said people in the newly eligible categories who were administered the Janssen vaccine should receive an mRNA booster dose after an interval of three months because it is “less effective” than a two-shot vaccine. Ireland ceased receiving deliveries of the vaccine in August; 155,000 people had received the vaccine by July 18th, four months ago.

Niac has also decided not to recommend the Moderna vaccine for eligible people aged under 30 years "as a precaution". A similar approach has been taken by authorities in France and the Scandinavian countries after early data showed a higher rate of myocarditis in young males who received Moderna compared to those who were administered Pfizer. This data is being examined by the European Medicines Agency.

Those aged 16-29 should be given a full dose of Pfizer vaccine at least six months after they received their primary course of any Covid-19 vaccine.

For those aged 30 and over, the Pfizer vaccine or a half-dose of Moderna should be administered after a six month interval, though for operational reasons a minimum interval of five months may be used.

Niac says there is early evidence the infection rate is slowing down among those aged 75-79 due to the administration of boosters. Covid-19 infections have already fallen among those aged 80 and over, where booster coverage is above 80 per cent. It also describes as encouraging a decrease in the number of infections among healthcare workers in the second half of October.

Niac says the current surge is likely due to the Delta variant, waning vaccine immunity and the opening up of society.

“It is essential that all recommended public health and social measures to limit Covid-19 exposure are observed. Booster doses will not immediately contribute to outbreak management nor take the place of public health and social measures,” it said.

Niac says it continues to examine new evidence regarding the durability of protection of primary vaccines in other groups, such as younger age groups who received the AstraZeneca or Janssen vaccines.

Chief medical officer Dr Tony Holohan has endorsed Niac's recommendations in a letter to Mr Donnelly. "There are currently no data on the long-term effectiveness of booster doses, so it remains unclear how long the benefit of boosters may persist, or the magnitude of the effect boosters have on transmission of the virus," he says in the letter.

Paul Cullen

Paul Cullen

Paul Cullen is Health Editor of The Irish Times