UPDATE 1-Brazil sets single-day record for coronavirus cases

(Adds context on outbreak, details of Senate investigation)

RIO DE JANEIRO, June 23 (Reuters) - Brazil registered a single-day record of 115,228 new confirmed coronavirus cases in the past 24 hours, the Health Ministry said on Wednesday, as its outbreak shows new signs of accelerating despite long-delayed vaccination efforts finally gaining steam.

Brazil has recorded the world's highest COVID-19 death toll outside the United States, with more than half a million lives lost, according to the ministry's official tally.

But while the situation in the United States and most wealthy nations improves thanks to higher vaccination rates, Brazil and many neighbors in South America this month have seen their biggest outbreaks yet.

Brazil's seven-day average for new coronavirus cases and deaths is now the highest in the world, having surpassed India last week, according to data compiled

by Reuters.

Brazil marked the milestone of 500,000 COVID-19 deaths over the weekend with nationwide protests against the government's handling of the pandemic.

The country has been slow to roll out vaccines with only 12% of Brazilians fully immunized, according to Health Ministry data. Efforts have accelerated recently, with certain states such as Sao Paulo predicting shots for all adults by September.

The government of President Jair Bolsonaro is under scrutiny for delays and alleged misconduct in obtaining vaccines, having failed to respond to early offers from Pfizer last year.

The government instead struck a deal for more a expensive vaccine made by India's Bharat Biotech.

A Senate committee is probing allegations related to Bharat amid a wider investigation of the government's response.

A Brazilian Health Ministry official told prosecutors he faced internal pressure from an aide to then-Health Minister Eduardo Pazuello to buy the Bharat shot.

In a press briefing on Wednesday, Bolsonaro's Secretary of the Presidency Onyx Lorenzoni said there had been no influence peddling in the Bharat deal and the vaccines were not overpriced.

The Health Ministry did not respond to request for comment about the allegations.

On Wednesday, the committee also called representatives of Facebook , Google and Twitter to testify before the committee as it weighs possible crimes related to misinformation online about COVID-19.

(Reporting by Pedro Fonseca Additional reporting by Jake Spring Editing by Brad Haynes and Lincoln Feast.)

((jake.spring@thomsonreuters.com; +55 61 99653-2429; Reuters Messaging: jake.spring.thomsonreuters.com@reuters.net / Twitter: ))