Sao Paulo, Rio de Janeiro and other Brazilian states on Tuesday suspended immunization of pregnant women with the AstraZeneca coronavirus vaccine on the advice of the national health regulator after a reported death.

The suspension was to remain in place until the health ministry establishes the cause of death of a woman in Rio de Janeiro who received the vaccine, Health Minister Marcelo Queiroga told a news conference.

Queiroga said the call was made by a team of experts and was based "exclusively on technical criteria."

"It is not clear that the vaccine caused this blood clot. We are analyzing the details of the whole case to reach a conclusion and clarify what happened," said Jorge Kalil, a consultant for the National Vaccination Program, who took part in the press briefing.

Brazil's health regulator, Anvisa, recommended late Monday the "immediate suspension" of AstraZeneca vaccines for pregnant women in line with its "constant monitoring of adverse events with anti-Covid vaccines used in the country."

Franciele Francinato, coordinator of the National Vaccination Program, said pregnant women who had already received the first dose of AstraZeneca should hold off getting the second shot until the ministry issued new guidelines.

The Rio de Janeiro municipal health secretariat said in a statement that authorities had decided to suspend application of the vaccine to pregnant women and new mothers in the state capital "until the investigation of the case of an adverse event in a pregnant woman is completed by the Ministry of Health."

Other municipalities in the state adopted the same measure, and Sao Paulo state said it would also stop vaccinating women with comorbidities.

Nurse Janete Da Silva Oliveira prepares a dose of Oxford-AstraZeneca Covid-19 vaccine in the Nossa Senhora Livramento community on the banks of the Rio Negro, near Manaus, Amazonas state, Brazil February 09, 2021.
Nurse Janete Da Silva Oliveira prepares a dose of Oxford-AstraZeneca Covid-19 vaccine in the Nossa Senhora Livramento community on the banks of the Rio Negro, near Manaus, Amazonas state, Brazil February 09, 2021. AFP / MICHAEL DANTAS

In all, 22 of Brazil's 27 states have taken similar steps, reported news site G1.

AstraZeneca said in a statement that pregnant and nursing mothers had been excluded from its vaccine tests, which it said was common practice in clinical trials.

"There were no adverse effects related to pregnancy observed in studies on animals," it said.

Several European countries have restricted AstraZeneca shots to older people only, after a link was made between the vaccine and very rare but often fatal blood clots coupled with low platelet levels.

Denmark has abandoned the vaccine entirely and experts in Britain have recommended people under 40 be given an alternative.

Brazil is immunizing the bulk of its population with China's CoronaVac, with limited doses of AstraZeneca and Pfizer vaccines.

The AstraZeneca shot represents about 26 percent of all doses administered in the country so far.

The Latin American giant of 212 million people has given one shot to 15 percent of its population, and two shots to seven percent.

It has been hit hard by Covid-19, with a death toll of more than 423,000, second only to the United States.

Coronavirus