Mass vaccination experiment was a huge success in Brazil

By vaccinating almost all adults, one town cut its COVID-19 deaths by 95%.

The preliminary results of a mass vaccination experiment in Brazil suggest that even a moderately effective vaccine can dramatically reduce COVID-19 cases and deaths — if everyone who can gets vaccinated.

The background: Sinovac Biotech was an early frontrunner in the race to develop a COVID-19 vaccine, demonstrating an ability to protect animals from the disease back in April 2020.

However, the results of late-stage human trials of the vaccine were both somewhat underwhelming and puzzling — depending on the trial, the efficacy ranged from just above 50% to an impressive 91% to a middle-of-the-road 65%.

It was already December by the time those results were rolling in, and the shot, called CoronaVac, was largely overshadowed — at least in the U.S. and Europe — by the authorization of other, more consistently effective vaccines.

The experiment: In an attempt to determine the real-world effectiveness of CoronaVac, researchers at Butantan Institute (a research center in São Paulo) launched a mass vaccination experiment in hard-hit Brazil.

The plan was to see what would happen if nearly every adult in the town of Serrana received the CoronaVac vaccine (excluding only pregnant women and people with chronic diseases).

Within two months, the researchers had administered two doses of the vaccine to 96% of those eligible and old enough to receive it — that translated to about 27,000 of Serrana’s 45,000 residents, or 60%.

The preliminary results: Since the launch of the mass vaccination experiment in February, the number of symptomatic COVID-19 cases in Serrana has dropped by 80%, the researchers reported on May 31. Coronavirus-related hospitalizations are down 86%, and deaths have decreased by 95%.

Meanwhile, the pandemic has continued to rage in nearby Brazilian cities.

“Serrana is now an oasis,” Ricardo Palacios, a Butantan Institute epidemiologist, told Science Magazine. “And it has shown us that it is surely possible to control the epidemic through vaccination.”

The next steps: The results of the mass vaccination experiment have yet to be peer-reviewed or published, but the WHO validated the vaccine for emergency use the day after the researchers’ announcement.

Serrana is now an oasis.

Ricardo Palacios

That means CoronaVac can now be distributed through COVAX, an initiative to get vaccines to people in low- and lower middle-income countries. This news is particularly welcome given that CoronaVac, a traditional inactivated vaccine, should be far easier to distribute than several other WHO-validated vaccines.

“The easy storage requirements of CoronaVac make it very suitable for low-resource settings,” WHO Director-General Tedros Adhanom Ghebreyesus told reporters. “It’s now crucial to get these lifesaving tools to the people that need them quickly.”

We’d love to hear from you! If you have a comment about this article or if you have a tip for a future Freethink story, please email us at [email protected].

Bird flu is everywhere. Are the vaccines ready?
As avian influenza continues to devastate the bird population and jump into mammals, scientists are preparing to protect two important groups.
What that study linking sugar-free sweeteners and heart disease really tells us
A new study links higher blood levels of sugar-free sweeteners, commonly found in ketogenic diet foods, to a greater risk of death.
As bird flu spreads in the US and worldwide, what’s the risk that it could start a human pandemic?
Many virologists are concerned that the latest bird flu outbreak could spill over to humans and cause a new human pandemic.
This easy fix could eliminate harmful chemical exhaust from home heaters
Retrofitting gas heaters with this catalyst could slash their environmental impact.
Making electricity from wastewater
Researchers have developed a “sandwich-like” membrane that removes pollutants while generating power.
Up Next
inhaled nanobodies COVID-19
Subscribe to Freethink for more great stories