Delta, a new challenge for collective immunity

New modeling by scientists at James Cook University shows that Australia must vaccinate at least 85% of its population to achieve herd immunity.

Emma McBryde, professor of infectious disease epidemiology and modeling at the Australian Institute of Tropical Medicine at the JCU (AITHM), said the modeling had an impact on the federal government’s four-step plan to move from suppression from COVID to recovery and reversion strategies. Normal life.

“The first hurdle is to vaccinate to reach the herd. However, herd immunity is more infectious and less sensitive to vaccination, which makes it more difficult to achieve with delta mutants,” explains Professor McBride.

She said the AITHM team will work with countries in our region to study and optimize herd immunity thresholds. Vaccine distribution Repeated the movement across the world for the original Wuhan strain, and now for the Delta variety.

“Assuming the number of Delta Variant 4 reproductions (the number of people infected with the virus), this shows that 85% of the Australian population needs to be vaccinated using current strategies. “We are doing it,” said Professor McBryde.

She said Australia can achieve herd immunity by vaccinating 75% of the population when the vaccine is targeted at the most infectious ages. However, this may not be realistic. This is because the 20 to 60 year old age group requires almost 100% assimilation.

“We have also shown that even without herd immunity, vaccinated people are protected against serious illness and are much less likely to be hospitalized or die,” said Professor McBride.

She said the AITHM team concluded that the delta variant makes it very difficult to obtain herd immunity.

“But it’s important to remember that as we approach Australia, both vaccinated and unvaccinated people reduce their risk of infection and disease. Collective immunity .. ”