Covid-19 vaccines made by Pfizer and AstraZeneca (AZ) were proved to be protective against the Delta coronavirus variant, first identified in India, a Scottish study showed.

Patients infected with the Delta variant were twice as likely to be hospitalized compared to those who contracted the Alpha variant, the study said.

The research team at the Public Health Scotland used EAVE II, a Scotland-wide Covid-19 surveillance platform, to conduct a cohort analysis and published the results in The Lancet on Monday.

The analysis covered the period from April 1 to June 6. During the period, 19,543 people were confirmed with Covid-19, and 377 were admitted to medical institutions. As of April 1, 44.7 percent of the Scottish population received the first dose of a Covid-19 vaccine, and 7.6 percent, the second dose.

The analysis results showed that the Delta variant was found mostly in younger generations. The risk of hospitalization doubled in those with the Delta variant compared to those with the Alpha variant.

Both the AZ and Pfizer vaccines were effective in preventing the Delta variant infection. The protective effect appeared a while after the second shot.

The Pfizer vaccine was 79 percent effective against the Delta variant and 92 percent against the Alpha variant at least 14 days after the second dose. The AZ vaccine was 60 percent effective against the Delta variant and 79 percent against the Alpha variant.

Earlier, Public Health England released similar study results. The study said two full doses of the Pfizer vaccine reduced the chance of hospital admission for the Delta variant infection by 96 percent. Two doses of the AZ vaccine lowered the risk of the infection progressing to a serious disease by 92 percent.

Novavax, a U.S. biotech firm, said its Covid-19 vaccine candidate showed over 90 percent effectiveness in a phase-3 trial in 30,000 participants in the U.S. and Mexico. The investigational vaccine was also 93.2 percent protective against major coronavirus variants, but its effect on the Delta variant has yet to be known.