text: US vaccine protects macaques from Covid-19
  Animals injected with vaccine developed by Boston team show much lower levels of infection after being exposed to pathogen and 'near-complete protection' on second exposure
  /NOVOSTIVL/ Vaccines developed by scientists in the United States have been shown to be effective in protecting monkeys against the coronavirus that causes Covid-19. This article appeared in SCMP.
  Researchers from the Beth Israel Deaconess Medical Centre (BIDMC) in Boston, Massachusetts carried out two studies using six DNA vaccine candidates they have been working on since January – when Chinese scientists released the viral genome – each of which uses a different variant of a key viral protein.
  The results were published on Wednesday in the peer-reviewed academic journal Science.
  In the first study, the researchers injected 25 adult rhesus macaques with a vaccine, while 10 others were given a sham control – similar to a placebo – for comparison purposes.
  Three weeks later, all of the animals were exposed to SARS-CoV-2 – the formal name for the novel coronavirus.
  Of the vaccinated monkeys, eight showed no detectable signs of being infected, while the rest had only low levels of infection, which showed that the vaccines had induced neutralising antibody responses in the animals, the report said. By comparison, the non-immunised group had much higher viral loads.
  The researchers said the higher antibody levels were linked to lower viral loads, suggesting that the antibodies were effective for protection and could prove useful as a benchmark in clinical tests for vaccines. According to a statement issued by the BIDMC, the vaccines express variants of the spike protein – an antibody that targets the coronavirus – and are designed to train the body's immune system to recognise and respond quickly to the pathogen.
  Dan Barouch, director of the centre for virology and vaccine research at the BIDMC and the studies' lead author, highlighted the importance of research into coronavirus vaccines.
  "The global Covid-19 pandemic has made the development of a vaccine a top biomedical priority, but very little is currently known about protective immunity to the SARS-CoV-2 virus," he said.
  In the second study, the researchers showed that macaques that had recovered from Covid-19 also developed antibodies to protect against repeat infection.
  More than a month after the initial infection, the team re-exposed the monkeys to the virus, but on second exposure, they showed near-complete protection against the coronavirus.
  The model suggested natural protective immunity against the disease, the BIDMC said.
  "Our findings increase optimism that the development of Covid-19 vaccines will be possible," Barouch said.
  "Further research will be needed to address the important questions about the length of protection, as well as the optimal vaccine platforms for a SARS-CoV-2 vaccine for humans".
  Earlier this month, a team of Chinese scientists developed a purified inactivated vaccine candidate that provided macaques with partial or complete protection against the virus.
  "These data support clinical development of SARS-CoV-2 vaccines for humans," they said in a report, also published in Science.