The Russian sovereign wealth fund backing the country’s Sputnik V coronavirus vaccine said the decision from Brazil’s health regulator not to authorise imports of the jab was politically motivated.

Brazilian officials late on Monday rejected a request to import the vaccines made by state governors in Latin America’s largest nation, which is still fighting a second wave of the Covid-19 pandemic and has faced supply shortages in its inoculation campaign.

Anvisa, the country’s healthcare and medicines watchdog, cited risks with Sputnik V and said there was not enough information about its safety, effectiveness and quality. It added that failings were identified in the development of the product and all stages of clinical studies.

“All of these uncertainties can directly interfere with the control of the pandemic in our country, because if the vaccine’s efficacy is not adequate, it can generate a false sense of security,” Anvisa director Alex Machado Campos wrote in his report.

The decision deals a blow to Russia’s efforts to further boost exports of the vaccine, which has been built around sales to large emerging market nations such as Brazil. Developed by the Russia’s state-run Gamaleya Institute, Sputnik V has been approved by Moscow and 60 foreign governments.

The two-shot vaccine showed 91.6 per cent efficacy against symptomatic Covid-19 in clinical trials, a Lancet peer review confirmed this year. A consortium of states in north-east Brazil had already agreed to buy 37m doses, while the federal government has an order for 10m.

Sputnik V’s backers accused the Brazilian health agency of bowing to political pressure from the US to block Russian vaccines, insisting that all necessary documentation and information had been shared with the authorities.

“Anvisa’s delays in approving Sputnik V are, unfortunately, of a political nature and have nothing to do with access to information or science,” the Russian Direct Investment Fund, which is managing Sputnik V’s global sales, wrote on a Twitter.

“We hope that science, not pressure from another country, will be used for decision making,” it said.

Anvisa said its agents were not permitted to undertake an inspection of Gamaleya Institute facilities during a visit to Russia last week.

Another concern highlighted by the agency was related to the adenovirus vector, the common virus used to carry the genetic code of a part of Sars-Cov-2 in the Sputnik vaccine, as well as the AstraZeneca and Johnson & Johnson shots.

Anvisa said the presence of adenoviruses with the ability to replicate — a naturally occurring process that has to be neutralised for immunisations — had been detected, which can “lead to infections in humans and could cause damage and death, especially in people with low immunity and respiratory problems, among other health problems”.

RDIF said in a statement that Anvisa’s decision “contradicts an earlier decision by Brazil’s Ministry of Science . . . which recognised the Sputnik V vaccine as safe and permitted its production in Brazil”. Anvisa’s team in Moscow “had full access to all the relevant documents as well as to research and production sites”, it added.

On Tuesday, RDIF said: “The Gamaleya Center, which carries out strict quality control of all Sputnik V production sites, has confirmed that no replication-competent adenoviruses (RCA) were ever found in any of the Sputnik V vaccine batches that have been produced.”

The ruling threatens to slow Brazil’s vaccination programme, which has delivered at least one dose to roughly 27.5m people, or 12.9 per cent of the population. Most have received the Chinese-developed CoronaVac shot. The Oxford/AstraZeneca jab is also being deployed.

However, repeated delays in shipments of pharmaceutical ingredients from overseas for producing both vaccines domestically has dragged on distribution, as Brazil’s Covid-19 death toll nears 400,000.

“The refusal by Anvisa [to authorise Sputnik imports] will lead to a big reduction in the number of doses estimated under the national immunisation programme,” said Fernando Aith, a professor of public health at the University of São Paulo. “Millions of doses for the states and city halls will no longer enter the country.”