Harvard scientists have published two studies that seek to understand whether immunization can prevent Covid-19 and whether antibodies produced by the body can fight the infection.
In the fight against Covid-19, two questions keep coming up: is there a vaccine capable of preventing infection with the new coronavirus? And do people who have had the disease develop immunity against it? In two new studies published on Wednesday (20) in the journal Science, scientists at the Beth Israel Deaconess Medical Center, a teaching hospital of Harvard Medical School, in the United States, are investigating possible answers.
In the first study, the team demonstrated that six different vaccine candidates can induce immune responses, creating neutralizing antibodies and protecting against Sars-CoV-2. The researchers tested the drugs on 25 rhesus macaques and applied a placebo to ten other animals to serve as a control group.
According to the scientists, three weeks after a booster vaccination, the 35 primates were exposed to the new coronavirus. Follow-up examinations revealed that the vaccinated macaques had drastically lower viral loads than those who received the placebo: eight of the 25 vaccinated animals did not even show evidence of the presence of Sars-CoV-2 in their bodies.
In addition, animals that had higher antibody rates had lower levels of the virus. According to the authors, this suggests that neutralizing antibodies may be a reliable method of protection, which will be useful in clinical trials of vaccines against Covid-19.
Antibodies = immunity?
In the second study, nine rhesus macaques were exposed to Sars-CoV-2 and had their viral loads monitored. According to the scientists, all animals recovered and developed antibodies against the new coronavirus.
The researchers also assessed whether these primates could contract Covid-19 again – and the result was encouraging. After the second exposure to Sars-CoV-2, the animals showed almost complete resistance, suggesting that they developed a natural protective immunity against the microorganism.
This is not the first time that scientists have successfully tested a vaccine against Covid-19 in rhesus macaques, primates of the species Macaca mulatta, which lives in temperate forests in India, China and Afghanistan. At the end of April, a study carried out with another group of primates of this species by Chinese researchers was also successful.
“Further research will be needed to address the important questions about the length of protection as well as the optimal vaccine platforms for SARS-CoV-2 vaccines for humans,” says Dan H. Barouch, senior author of the studies published on Science this Wednesday, in a statement. “Our findings increase optimism that the development of COVID-19 vaccines will be possible.”