CANBERRA, Australia — Australia’s chief medical officer has warned real-world data will be needed to determine how effective one dose of the nation’s vaccines is against the Indian coronavirus strain.
Melbourne is in the midst of an outbreak of the variant, which has infected more than 50 people and plunged Victoria into lockdown.
A Public Health England study, ‘ Effectiveness of COVID-19 vaccines against the B.1.617.2 (Delta)variant,’ found last month two doses of AstraZeneca and Pfizer were 88 percent effective against the strain.
But that fell to 33 percent three weeks after a single dose.
The analysis included data for all age groups from April 5 to cover the period since the B.1.617.2 variant emerged. It included 1,054 people confirmed as having the B.1.617.2 variant through genomic sequencing, including participants of several ethnicities.
The difference in effectiveness between the vaccines after two doses may be explained by the fact that rollout of second doses of AstraZeneca was later than for the Pfizer-BioNTech vaccine, and other data on antibody profiles show it takes longer to reach maximum effectiveness with the AstraZeneca vaccine.
As with other variants, even higher levels of effectiveness are expected against hospitalization and death.
Chief Medical Officer Paul Kelly said he was wary of the “pre-print” study because it had not been peer-reviewed.
“Many of those articles have been proven to be false,” he said in a Senate estimates hearing on June 1.
Kelly claims that the data came from a laboratory study, and real-world information was needed to determine effectiveness against the Indian strain.
“We don’t know. We will know when we’ve had more experience.”
Health Department Secretary Brendan Murphy defended the effectiveness of a single dose.
“We don’t know. It may be that the vaccines are less effective against the Indian variant after one or two doses,” Murphy said.
“The point I was making, and this applies to all of the variants and vaccines, was that the first dose within weeks provides very good protection. That’s all the data we have.”
Murphy claimed that new strains could change vaccine efficacy.
“If in the Indian variant the vaccines are less effective after one dose, they’re probably less effective after two doses. We just don’t know that.”
The chief medical officer also confirmed there would be a need for booster shots to combat coronavirus variants of concern in the future.
(Edited by Vaibhav Vishwanath Pawar and Pallavi Mehra)
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