Cuba has begun a mass vaccination campaign using a home-grown vaccine that hasn’t yet completed large-scale human trials. The country has five covid-19 vaccines in development, with two in such phase III trials.

It is the smallest country to develop a promising vaccine candidate, and the only one in Central or South America to do so. Its ambition is to immunise its entire population with the vaccines – and with no doses of other shots on order, there is everything to lose.

Cuba began rolling out its Abdala vaccine in Havana on 12 May, with phase III trials still running, in what the country’s Ministry of Public Health labelled a “public health intervention” that will eventually reach 1.7 million people. The ministry has justified the roll-out based on the growing number of cases in the country and deems the vaccine to be safe based on trials so far. It hasn’t yet been fully approved for use by the national regulatory body.

Another vaccine, Soberana 02, which is also in phase III trials, is already being rolled out to 145,000 healthcare workers and researchers as part of a similar intervention to test the vaccine in high-risk populations.

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A successful vaccine could lift Cuba out of its worst economic and health crisis in decades. It has reported 112,000 cases of covid-19 and around 700 deaths. The toll is relatively small for the region, but cases have surged to more than 1000 a day since airports were reopened last November. There are even suggestions that a vaccine could be offered to tourists to entice them to return— a vital source of revenue for the socialist nation that is under US sanctions.

Other countries in the region are looking to Cuba too, as covid-19 cases continue to surge. Argentina, Bolivia, Honduras and Mexico are discussing the possibility of procuring or manufacturing Cuban vaccines. Venezuela is trialling the Abdala vaccine and hopes to produce 4 million doses.

The vaccines appear to be “very safe” as no severe adverse reactions were reported in phase II trials and because they are based on pre-existing vaccine technology, says Amilcar Perez Riverol at São Paulo State University in Brazil.

Phase III trials of Soberana 02 began in Havana on 8 March, and Abdala trials began on 22 March in Santiago de Cuba, Guantánamo and the province of Granma.

A phase II trial of Soberana 02 showed that it generated neutralising antibodies against the SARS-CoV-2 coronavirus in 81 per cent of vaccinated people who were given two doses, four weeks apart. Adding a third dose of a different vaccine, Soberana Plus, increased this to 96 per cent.

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“You hope in phase II to have the same levels of neutralising antibodies that you see in infected people who overcome the infection and the disease, and the data [shows] this is happening for both,” says Perez Riverol. “I’m pretty optimistic.”

Phase III trials of Soberana 02 are expected to conclude later this month. Neither Soberana 02 nor Abdala needs specialist refrigeration, but people may need to be given three doses of them.

That the 11-million-strong island is the leader in the regional vaccine race has raised eyebrows, but Cuba has a strong reputation for vaccinology, says Helen Yaffe, a historian at the University of Glasgow, UK, studying Cuba’s biotech history.

Cuba has eliminated five diseases through vaccination: polio, diphtheria, measles, whooping cough and rubella. It exports hundreds of millions of vaccine doses a year to more than 40 countries. Its biotech sector was set up by former president Fidel Castro and is based on a well-invested, collaborative model directed at public need rather than profit. “The different institutes don’t compete for resources and information, they share them and coordinate between themselves,” says Yaffe.

If Cuba succeeds in its efforts, it could bring much relief to the wider region, which is facing a scarcity of jabs while reporting 1 in 3 global covid-19 deaths. On 1 May, AstraZeneca announced there would be delays to manufacturing its vaccine in Central and South America.

However, if Cuba’s vaccines aren’t approved, or aren’t effective, it would be a disaster. Cuba isn’t engaged in negotiations with international pharmaceutical companies or with COVAX, a scheme co-led by the World Health Organization to help low and middle-income nations acquire vaccines.

Dagmar García Rivera at the Finlay Vaccine Institute in Cuba, which developed Soberana 02, is confident the high-risk strategy will pay off. “Betting on the development of our own vaccines rather than buying them was a strategic decision supported by the scientific and technological development of the Cuban biotechnology industry, and at the moment, we are on the way to prove that it was a wise one,” she says.