The Australian Technical Advisory Group on Immunisation (ATAGI) has asked people in Greater Sydney under the age of 60 to consider getting vaccinated against COVID-19 with AstraZeneca.
While Pfizer remained the preferable vaccine for people in the under-60 age group, ATAGI said those living in areas where there were COVID-19 outbreaks of the Delta variant should consider the option of getting an AstraZeneca vaccine immediately if they could not access the other mRNA shot.
On Tuesday the advisory group issued a statement that included a re-assessment of the AstraZeneca vaccine’s risks versus benefits during an outbreak.
“ATAGI reinforces that the benefits of vaccination with COVID-19 Vaccine AstraZeneca strongly outweigh the risks of adverse effects in those ≥60 years, and that vaccination is essential for this group in the context of an outbreak,” the statement read.
“In the context of a COVID-19 outbreak where the supply of Comirnaty (Pfizer) is constrained, adults younger than 60 years old who do not have immediate access to Comirnaty (Pfizer) should re-assess the benefits to them and their contacts from being vaccinated with COVID-19 Vaccine AstraZeneca, versus the rare risk of a serious side effect.”
To ensure that individuals avoided severe COVID-19 impacts, including the chronic health problems of long COVID or in the worst cases death, ATAGI said that the benefits of getting an AstraZeneca shot for those 60 and over were clear.
The risk that ATAGI refers to is the risk a person who has been vaccinated with AstraZeneca has of developing thrombosis with thrombocytopenia syndrome (TTS).
Cumulative estimates of the chances of getting the rare blood-clotting disease after vaccination have been calculated by ATAGI, according to age group. Their analysis showed that most of the adverse cases of the TTS occurred about two weeks after vaccination, with just over 1 in 4 cases requiring ICU treatment.
Sydney residents face heightened COVID-19 risk amidst Delta outbreak
The group recommended that people aged under 60 should should consider how the ‘risk-benefit balance’ had evolved in the midst of Sydney’s latest outbreak.
As at 11 July, ATAGI said the current cumulative risk that a Sydney resident would catch COVID-19 was approximately 10 per 100,000. That risk increased by an additional two cases per 100,000 people daily, the advice said.
“Although overall this is comparable to the Australian first wave (cumulative incidence 29 per 100,000), the ongoing risk would be considerably greater in some parts of Sydney and for specific populations.
“For example, in Fairfield Local Government Area, the cumulative risk to date is >100 per 100,000 and has increased by >10 cases per 100,000 per day in the past week.”
Vaccination remained a key public health intervention for Australia to tackle COVID-19, ATAGI stressed. With the community transmission of the COVID-19 Delta strain in Australia, the group warned that more infections would mean more people who contract the virus to be hospitalised and need treatment in an intensive care unit (ICU).
The group also advised that any unallocated supplies of either Pfizer or AstraZeneca should be distributed to prioritised groups and areas of greatest risk of COVID-19. They noted that a single vaccine shot was less effective protecting people from being infected by the Delta variant than receiving two boosters.
“The effectiveness of vaccination against infection with a single dose of COVID-19 vaccine, either Comirnaty (Pfizer) or COVID-19 Vaccine AstraZeneca is notably lower against infections with the Delta variant compared with other strains,” ATAGI said.
“A two-dose course of vaccination offers optimal protection against both infection and hospitalisation.”
Advice on time between AstraZeneca boosters changed for Sydney-siders
ATAGI further noted that its advice on the time between first and second doses had changed for Sydney.
The group said that people living with Sydney’s outbreak should seek out their second AstraZeneca vaccine dose between four and eight weeks from their first shot.
“People in an outbreak situation who received their first dose of COVID-19 vaccine AstraZeneca more than 4 weeks ago should contact their vaccine provider to arrange their second dose as soon as possible.
“In non-outbreak settings, the preferred interval between doses of COVID-19 Vaccine AstraZeneca remains at 12 weeks,” the group said.
ATAGI said it was the responsibility of jurisdictions where outbreaks were taking place to ‘determine when and where these recommendations are applicable’ and follow advice based on the current epidemiology of COVID-19.
“When the virus is spreading in the community it is critical that as many people as possible are vaccinated as quickly as possible.”