By Andrew MacAskill

LONDON (Reuters) -British Prime Minister Boris Johnson said on Monday that English nightclubs and other venues with large crowds will require patrons to present proof of full vaccination from the end of September.

Clubbers flocked on Monday to the first live music events without restrictions since the COVID-19 pandemic began. The government reopened nightclubs and dropped almost all coronavirus measures in England in a bet that mass vaccinations will prevent another deadly wave of COVID-19.

But later in the day, Johnson announced that people who were not fully vaccinated, including those who had not had both doses of two-shot immunizations, would be barred from nightclubs.

The decision follows large outbreaks linked to nightclubs in other countries such as the Netherlands and Israel, where authorities were forced to close them again.

“I can serve notice now that by the end of September when all over 18’s will have had their chance to be double jabbed, we’re planning to make full vaccination the condition of entry to nightclubs and other venues where large crowds gather,” Johnson told a press conference.

“Proof of a negative test will no longer be enough.”

Britain’s Chief Scientific Adviser Patrick Vallance said nightclubs and other closed venues could be “potential super spreading events” because of crowds in close contact.

“I would expect that with opening of nightclubs, we’ll continue to see an increase in cases, and we will see outbreaks related to specific nightclubs as well,” he said.

Johnson said that the government was not planning similar requirements for pubs. “I certainly don’t want to see passports for pubs,” he said.

(Reporting by Andrew MacAskill; Editing by Cynthia Osterman)