TAIPEI (Taiwan News) — The combination of AstraZeneca (AZ) and Moderna doses performs five times better than two AZ doses in fighting the highly-contagious Delta variant, a Taiwan study has found.

The findings are the results of a trial to determine the efficacy of mixing the two brands of vaccines against COVID-19, led by the National Taiwan University Hospital (NTUH) between June and August. The study involved 400 participants aged 20 to 65, 75% of whom were female.

Those who received two AZ shots registered antibody concentrations of less than 500 units after 14 days, while individuals who got AZ-Moderna jabs logged over 2,500 units. An antibody level of 4,000 units came back in those having two Moderna doses, according to the results published by the NTUH on Friday (Nov. 19).

Meanwhile, the AZ-Moderna pairing has also been found to generate greater potency against the Delta strain than two AZ doses. Two AZ doses have less than 20% efficacy against Delta, while two Moderna shots or AZ-Moderna shots both delivered 100% protection, CNA quoted Chang Shan-chwen (張上淳), convenor of the specialist advisory of the Central Epidemic Command Center (CECC), as saying.

While mixing the two vaccines is more likely to cause side effects, most of them were labeled as minor to moderate and did not last long. An eight-week interval between the two doses fares better than four weeks, with fewer adverse effects, said Sheng Wang-huei (盛望徽), deputy director of the NTU School of Medicine.