Scientist say giving the Pfizer vaccine to 12 to 40 year olds should be made a priority

Young people must get Pfizer priority to gain herd immunity Queensland scientists warn.

New modelling by Queensland scientists show that kids need to be vaccinated to reach herd immunity and the Pfizer jab should be made available to 12 to 40 year olds as a priority.

Epidemiologist Professor Emma McBryde and mathematician Dr Michael Meehan from James Cook University’s Australian Institute of Tropical Health and Medicine produced the model, published in the Medical Journal of Australia today.

Professor McBryde said the new model incorporates age-specific mixing, infectiousness, susceptibility and severity to assess the impact of the epidemic under different public health intervention scenarios.

“We have developed a simple, flexible online tool that is now being used around the world to develop vaccine implementation strategies. We’ve made it fully open-source to allow for the greatest transparency and examination of our methods,” Prof McBryde said.

Dashiel Farraway, 18, of Wynnum alongside partner Taylor Schroder, 18, of Holland Park as they both received their first dose of the Pfizer vaccine at the Brisbane Convention and Exhibition Centre. Picture: Zak Simmonds

She said the scientists investigated two alternative strategies for vaccine distribution. The first focused on vaccinating the vulnerable (people 55 and over) and the second prioritises vaccinating the most infectious (those under 55).

“We also produced results for AstraZeneca only, Pfizer only, and the current mixed program of vaccinating under 60 year-olds with Pfizer and 60 year-olds and older with AstraZeneca,” the professor said.

She said the modelling showed the current strategy of vaccinating the vulnerable older age groups first is the optimal strategy for reducing hospitalisations, deaths and years of life lost.

But she said there were uncertainties in the forecast, the most important hinging on the difficulty of establishing the effective reproduction number of the Delta Strain (the number of people one infectious person passes the virus on to).

Professor Emma McBryde, one of the Australia’s leading epidemiologists. Picture: Alix Sweeney

“Estimates range from three to seven. At the mid-range of most estimates, a reproduction number of five, at least 85 per cent of the population, including children, would need to be vaccinated to achieve herd immunity.

“So, the current plan to vaccinate 80 per cent of the adult population — or about 65 per cent of the total population — falls far short of herd immunity,” Prof McBryde said.

She said if the reproduction number is three, the current program can achieve herd immunity at 60-70 per cent coverage without vaccinating five-15 year-olds. But on the other side of the ledger, an effective reproduction number of seven means achieving herd immunity with existing vaccines would be impossible.

“We are unlikely to achieve herd immunity at the most plausible reproduction number of five unless vaccination is extended to younger ages or combined with other measures. Australia should now prioritise delivering Pfizer vaccine to 12-40 year-olds,” the professor said.

Originally published as Scientist say giving the Pfizer vaccine to 12 to 40 year olds should be made a priority