Preliminary study suggests CoronaVac neutralizes novel variants of SARS-CoV-2

Laboratory trial by Butantan Institute in partnership with the University of São Paulo involved inoculation of variants P.1 and P.2 into cultured cells containing blood serum from vaccinated subjects. The results were satisfactory, according to the researchers.

By Maria Fernanda Ziegler  |  Agência FAPESP – A preliminary study conducted by Butantan Institute in the state of São Paulo, Brazil, suggests the CoronaVac vaccine, developed by Chinese pharmaceutical company Sinovac Biotech, can neutralize variants P.1 and P.2 of SARS-CoV-2. Epidemiologists believe P.1, the more transmissible variant first detected in Manaus, is one of the causes of the recent jump in COVID-19 cases and deaths, alongside the relaxing of mobility restrictions in and after the holiday season and the slow pace of vaccination. 

“We’re all worried about the variants. We have to keep our eyes wide open and find out if the vaccines produce antibodies against them. We knew CoronaVac was provenly effective against the UK variant [B.1.1.7] and the South Africa variant [B.1.351]. Now we know it’s also effective against P.1 and P.2,” said Dimas Covas, head of Butantan Institute, during a press conference held on March 10 in the São Paulo State Government building.

Butantan Institute produces CoronaVac in Brazil and conducts clinical trials with support from FAPESP. 

“The study was conducted in partnership with the University of São Paulo [USP] in a biosafety level 3 [BSL-3] laboratory where the virus can be handled,” Ricardo Palacios, Butantan Institute’s Medical Director of Clinical Research, told Agência FAPESP. “In the analysis, we added P.1 and P.2 to a cell culture containing blood serum from vaccinated subjects. The result was highly satisfactory, albeit from a small number of samples. The antibodies present in the serum neutralized the action of variant P.1.”

P.1 was first reported publicly on January 10 by Japanese health officials after it was detected in four travelers from Brazil at Haneda airport in Tokyo. It is circulating widely in Brazil and is considered a “variant of concern” because it is much more transmissible. P.2 was first reported in Rio de Janeiro and is also circulating in Brazil but is not a variant of concern.

In the press conference, Covas stressed that the variants are new forms of the virus and some have alarmingly dangerous traits. “For example, B.1.17 [known as the UK variant] is 30% to 50% more contagious, and people infected with this variant are thought to be 30% more likely to develop the severe form of the disease,” he said. “In the case of B.1.351 [the South Africa variant], those infected have a higher viral load, it’s also more transmissible, and it’s resistant to neutralization by the antibodies produced by some vaccines and by prior natural infection. P.1 has the same key mutations as the UK and South Africa variants.”

Palacios welcomed the satisfactory results of the CoronaVac trial. “However, it will be important to put the result of this laboratory trial alongside the response we’re seeing in the elderly people who were vaccinated in February,” he said. “This real-world response data, which is also preliminary, indicates that the vaccine is effective against the circulating variants.”

According to statistics from the City of São Paulo, despite the sharp rise in cases of COVID-19 there, deaths of over-90s dropped 70% to 38 in February from 127 in January. Hospitalizations also fell sharply in this age group, which had recently been vaccinated. 

In the state of Pernambuco, the local health authorities also reported a fall in the number of requests for intensive care beds for over-85s.

Immune response

Laboratory trials involving cultured cells and blood serum from vaccinated subjects focus on the antibody immune response. “In this kind of trial, we can only analyze humoral immunity mediated by antibodies,” Palacios explained. “We know vaccine-induced immunity is much more robust, so the real-world response may be even better than the trial result. Only more trials can show if this is the case, as we’re now doing in Serrana.”

Serrana is a small-size city in São Paulo where on February 17 Butantan Institute began measuring the impact of COVID-19 vaccination. Everyone over 18 was to be vaccinated, and the researchers were to measure the impact of vaccination on viral transmission, including the reduction in demand for hospital beds, as well as its indirect effects on the economy, mobility, and novel variants of the virus.

Genomic data obtained in Serrana so far points to P.1 and P.2 as the most prevalent viral strains in January and February. “We’re conducting the Serrana project and tracking the evolution of the virus since June 2020. Changes in the virus appeared in December, and in January P.2 was already predominant in the city. Then P.1, which is more aggressive, took over. What happened in Serrana may have happened in other cities all over Brazil,” Covas said (read more at: agencia.fapesp.br/35416). 

“We’re also very interested in observing the impact of vaccination in Colombia, which bought CoronaVac directly from Sinovac in China. Colombia’s national vaccination plan prioritized the country’s Amazon region, which includes the border with Brazil. P.1 emerged in the Amazon, so we want to know more about what’s happening there. We could collect more evidence that CoronaVac neutralizes this variant of concern.”

A study by the University of Campinas (UNICAMP, in the state of São Paulo) showed natural immunity to be about six times less effective at neutralizing P.1 than at neutralizing the B-lineage prevalent in Brazil in the early months of the pandemic. It also showed that blood plasma from people vaccinated with CoronaVac was not highly effective at neutralizing B-lineage or P.1, but this was based on only eight samples (read more at: agencia.fapesp.br/35415).