Australia’s Delta outbreak shows vaccines protect against hospitalization
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4 min read . Updated: 11 Jul 2021, 01:42 PM IST - Figures are in line with evidence from other countries, including the U.K. and Israel
Early data from Australia’s outbreak of the Covid-19 Delta variant suggest that two vaccine doses offer significant protection against severe illness and hospitalization.
Health authorities in Sydney, Australia’s most populous city that is currently under lockdown because of its Delta outbreak, said Saturday that no one who has received two doses of a vaccine needed to be hospitalized. Of the 47 people in the hospital, 37 haven’t been vaccinated, according to data provided on Saturday.
Four people who were in the hospital got one dose of the AstraZeneca PLC vaccine and one person got one dose of the Pfizer Inc.-BioNTech SE vaccine. The other five people received two Pfizer-BioNTech doses—but they are nursing-home residents who were admitted as a precautionary measure.
“Two doses of either the AstraZeneca or the Pfizer vaccine is incredibly effective at preventing hospitalization and death, which is an incredibly positive contribution," said Kerry Chant, the chief health officer for New South Wales state, which includes Sydney.
The figures from Australia are in line with evidence from other countries, including the U.K. and Israel, showing that vaccines offer a high degree of protection against severe illness from the Delta variant. Recent data from Israel, though, showed the Pfizer vaccine is less effective at protecting against infection from the Delta variant when compared with previous strains, posing a challenge for health authorities as many countries ease coronavirus restrictions as vaccination programs progress.
“Conclusions we can tentatively take from these small NSW numbers is that our experience is likely to be similar to that reported in other countries with larger sample sizes," said Alex Martiniuk, an epidemiologist and professor at the University of Sydney. That “just underscores the need to vaccinate, quickly, and two doses."
Despite being small by global standards, Sydney’s outbreak provides a view into how quickly the Delta variant can spread in a lightly vaccinated population despite lockdown measures, mask mandates and social distancing. More than 550 people have fallen ill since the outbreak began in mid-June and new cases have climbed in recent days even though the city has been locked down for two weeks.
On Sunday, authorities said another 77 people were infected locally, up from the 50 reported on Saturday. They expected more than 100 new cases to be reported on Monday. Officials also said Sunday that a woman in her 90s had died, the first death tied to the current outbreak.
Just 8% of Australia’s population has been fully vaccinated, according to Our World in Data, compared with roughly half in the U.S. and the U.K. and 60% in Israel. Australia has successfully controlled the virus in the past by closing its borders and requiring returning citizens to quarantine in hotels. But its vaccine rollout has been slow in part because the AstraZeneca vaccine—which can be made in Australia—was deemed inadvisable for people under 60 due to fears about rare blood clots.
One concern for authorities is the number of relatively young people who have become seriously ill. Eight of the 47 people who were in the hospital are under 35 and four of the 16 people in intensive care are younger than 50. One person who was in intensive care is a teenager.
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One factor could be that people under 40 are generally not yet eligible to be vaccinated, as Australian authorities focus first on front-line workers and older people, who are considered to be at higher risk of severe illness. Australian officials have said they would like all adults to receive at least their first vaccine dose by the end of the year.
Sydney’s lockdown is supposed to end on July 16, but officials have said it is likely to be extended. One key metric is whether contact tracers can quickly find close contacts of confirmed cases and have them isolate at home so they don’t spread the virus to others. Officials said Friday that 14,000 people have been considered close contacts and were told to isolate. But on Saturday, they said that 37 of the 50 new cases were out and about for all or part of their infectious period.
“What we are seeing is chains of transmission and we’re having difficulty getting ahead of those chains," Dr. Chant said Saturday. “We need everyone to stay hunkered down this weekend."
Write to Mike Cherney at mike.cherney@wsj.com
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