LONDON (AP) — The U.K.'s COVID-19 vaccination program is beginning to break the link between infection and serious illness or death, according to the latest results from an ongoing study of the pandemic in England.

Researchers at Imperial College London found that COVID-19 infections dropped about 60% in March as national lockdown measures slowed the spread of the virus. People 65 and older were the least likely to be infected as they benefited most from the vaccination program, which initially focused on older people.

The study also found that the relationship between infections and deaths is diverging, “suggesting that infections may have resulted in fewer hospitalizations and deaths since the start of widespread vaccination.”

The positive news came amid renewed scrutiny of vaccinations that followed revised UK government guidance Wednesday that it will offer people under 30 an alternative inoculation to the AstraZeneca shot where possible. The change followed studies that the shot may be linked to very rare blood clots.

Health Secretary Matt Hancock told Sky News that the public should reassured by the abundance of caution demonstrated by authorities to make sure the vaccine rollout is as safe as possible.

“What we’ve learned in the last 24 hours is that the rollout of the vaccine is working, we’ve seen that the safety system is working, because the regulators can spot even this extremely rare event — four in a million — and take necessary action to ensure the rollout is as safe as it possible can be,'' he said. “And we are seeing that the vaccine is working. It’s breaking the link between cases and deaths.”

Some 31.7 million people had been given a first dose by Tuesday, or just over 60% of the country's adult population.

But Imperial researchers also urged caution, saying that infection rates leveled off at the end of the study period as the government began to ease the national lockdown and children returned to school. Future rounds of the study will assess the impact that further easing of restrictions has on infection rates.

The next step in lifting England’s third national lockdown is scheduled for April 12, when nonessential shops will be allowed to reopen, along with hair salons, gyms and outdoor service at pubs and restaurants.

The findings are based on data gathered by the 10th round of Imperial College’s Real-Time Assessment of Community Transmission study, which conducts swab tests on a random sample of people across England each month. The latest round tested more than 140,000 people from March 11 to March 30.

Even though Britain has had one of the world's fastest vaccine rollouts, its death toll from the pandemic is the highest in Europe at over 127,000.

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