Expert Urges Australian States to Reduce Pfizer Dose Intervals

By Marina Zhang
Marina Zhang
Marina Zhang
September 27, 2021 Updated: October 3, 2021

A leading Australian epidemiologist has urged the New South Wales (NSW) and Victorian state governments to return the Pfizer dose interval from 6 weeks to 28 days so that more young adults under 40 can receive their second vaccination.

Speaking to ABC News Breakfast on Sept. 27, Marylouise McLaws, epidemiologist and professor at University of New South Wales (UNSW), said: “There’s only one small study that had nearly 300 healthcare workers who hadn’t ever had an infection, and they looked at extending that dose.”

McLaws said that the extended vaccination dose intervals mostly “worked well during the Alpha (variant) period in England, but not Delta (variant).”

NSW and Victorian governments have been encouraging dose intervals of 6 weeks so that limited vaccine supplies would be redirected for the unvaccinated to obtain first dose protection in outbreak areas of greatest need.

The comments by Mclaws come after the publication of conflicting studies around COVID-19 vaccines.

One study by the University of Oxford suggests that although the Pfizer vaccine has greater efficacy, it is less effective over time.

Another study by the British Medical Journal (BMJ) has shown that the first shot of Pfizer has an efficacy of around 52 percent, with the second shot of approximately 95 percent.

However, a paper published (pdf) in the New England Journal of Medicine showed that in participants of 18 to 64 years, protection against infection was reduced by 22 percent every 30 days from the second vaccination with smaller reductions for the AstraZeneca vaccine. However, the study concluded that there was no suggestion that dosing intervals affected the efficacy of the vaccine and that younger adults were more protected.

A smaller UK based study (pdf) consisting of 503 healthcare workers in England demonstrated that those with a dose interval of six to fourteen weeks have a more sustained T immune cell activity than those with a dose interval of three to four weeks–the recommended period.

Currently, just over 47 percent of Victoria’s above 16s population is doubled dosed whilst NSW sits at around 60.1 percent. Nationally 51.5 percent of young adults 16 and over have been double vaccinated.

On Monday, Sept. 27, Victoria recorded 705 new local cases and one death. In NSW, there were 961 infections and nine deaths on Sunday, Sept. 26.

Both the Victorian and NSW governments have plans to ease restrictions once vaccination targets are met.

The federal government also has asked states to open up their borders before Christmas once vaccination rates reach 80 percent.

Marina Zhang