The AstraZeneca COVID-19 vaccine is no longer recommended for use as a booster dose according to updated advice from the Australian Technical Advisory Group on Immunisation (ATAGI).
In a statement, the Advisory Group said the vaccine was not recommended for use as a booster dose for people who had received a primary vaccination course of the AstraZeneca vaccine, including for those who were severely immunocompromised.
“However, it can still be used for this purpose in individuals who decline receiving an mRNA vaccine as a booster dose,” ATAGI said.
“There is no requirement for people who have already received a booster dose of AstraZeneca COVID-19 vaccine to receive an additional dose of mRNA vaccine,” it said.
ATAGI said the only scenario in which a booster dose using AstraZeneca was actively recommended was for people with medical contraindications to the Pfizer and/or Moderna vaccines, like anaphylaxis or myocarditis.
The Advisory Group also released updated evidence on the effectiveness of booster doses against the COVID Omicron variant.
It said that since the emergence of the Omicron variant in December, it had become apparent that waning protection against COVID-19 after two doses of vaccine was more rapid and pronounced than previously thought.
“Strong evidence suggests that booster doses of COVID-19 vaccines may enhance protection against symptomatic disease due to the Omicron variant,” it said.
“A substantial increase in the protective effectiveness against symptomatic disease and infection by the Omicron variant was observed after a booster dose.”
ATAGI said recent data from England showed that following a booster dose of mRNA vaccine, the effectiveness against symptomatic disease was restored to 50-75 per cent for the first three months, then 40-50 per cent between four to six months after the booster dose.
It said these figures were similar across groups which had received AstraZeneca, Pfizer or Moderna in the primary course.
“The booster dose of an mRNA vaccine was between 80-95 per cent effective against hospitalisation due to infection with Omicron variant for the first three months after boosting and 70-85 per cent effective four to six months after boosting,” the Advisory Group said.
“Furthermore, strong protection against death due to the Omicron variant for the first three months after boosting was seen with vaccine effectiveness at 85-99 per cent,” ATAGI said.
