Thousands of people aged under 50 could be given a mixed vaccine against Covid-19, under a new approach being considered by the National Immunisation Advisory Committee (Niac).
The vaccination programme could be changed to allow under-50s who have received a first dose of AstraZeneca to be given the Pfizer or Moderna vaccines as a second dose, Niac has told chief medical officer Dr Tony Holohan.
Niac also says it is keeping under review whether or not the interval between AstraZeneca shots should be cut from 12 weeks to eight, and is also looking at the vaccination of children with high-risk medical conditions.
Earlier this year, after rare but serious blood clots were found in people who had received the AstraZeneca vaccine, Niac recommended mRNA vaccines (Pfizer or Moderna) for under-50s.
However, at least 40,000 people, many of them healthcare workers, have already received a first dose of AstraZeneca and are awaiting a second dose.
Niac says there is now published evidence of the safety of “heterologous” vaccine schedules, in which doses of two different vaccines are administered against Covid-19.
At its meeting this week, Niac examined emerging data on very rare clotting events linked to AstraZeneca.
Niac has told Dr Holohan in a letter it will review the safety of mixing vaccines as well as unpublished evidence of effectiveness.
In the UK, the interval between doses of the AstraZeneca and mRNA vaccines has been cut from 12 weeks to eight due to the rise in Indian variant cases. In Ireland, the interval for mRNA vaccines is four weeks while for AstraZeneca it is 12 weeks.
