The result came out at a time when the world is once again battling against the Delta variant.

The results were published just as Hungarian Prime Minister Viktor Orban’s government, which has faced opposition criticism for having widely administered Sinopharm shots to older people, started offering third shots this week for anyone who requests them, reports Bloomberg.

Hungary, which has been badly hit by COVID-19, remained the only European Union country to have deployed the Sinopharm vaccine to combat Covid-19.

The non-representative study tested 13,524 people who were at least 60 years old. More than half had been inoculated with Sinopharm, reports Bloomberg.

The results showed that 25.9% of those people didn’t have the minimum antibody level of 50 AU per milliliter, compared with 3.2% for those who received Russia’s Sputnik V, 1.6% for Pfizer-BioNtech and 1.1% for Moderna.

Sinopharm’s ability to generate antibodies got progressively worse with age, with vaccinated people who didn’t have the minimum antibody level rising to 34.5% among those aged 80 and over, the results showed as quoted by Bloomberg.