Two new, interrelated studies in macaques show, according to the researchers involved, that vaccination basically protects the animals against infection with SARS-CoV-2. Both studies appeared in Science.
Abishek Chandrashekar et al. tested nine adult animals that were infected with the virus but found no virus particles when they were re-exposed to the virus 35 days later. They were found to be protected from the second infection. In a second examination from almost the same team (Jingyou Yu et al.) an experimental vaccine expressing six different forms of the SARS-CoV-2 spike protein was tested. That is the protein that is known to be used by SARS-CoV-2 to invade cells. Yu et al. Vaccinated 35 macaques, which were infected intranasally with SARS-CoV-2 six weeks later. Result: they were found to have enough antibodies to effectively neutralize the virus within two weeks.
The much talked about Oxford vaccine – a weakened version of an adenovirus that causes respiratory infections in chimpanzees and has been genetically altered to produce a coronavirus protein – protected monkeys from pneumonia. Remarkably, however, the noses of the animals still contained as much SARS-CoV-2 as those of unvaccinated monkeys. Nevertheless, a phase I trial with healthy adult volunteers started in April. More than 1,000 immunizations have been completed and follow-up is currently underway. After this, 250 people will be recruited, with participants receiving either one or two doses of the vaccine or a meningitis vaccine acting as a control.
In addition, the biotech company Moderna announced the first results of an RNA-based vaccine this week. The company says researchers have identified antibodies in 25 subjects; the levels would be similar to those in the blood of people who have recovered from covid-19. The only question is what that says: it is uncertain whether people with mild disease have enough neutralizing antibodies to cope with a second infection. The same doubt may also apply to the Oxford vaccine. It always applies: it is not all gold that shines.
Moderna nevertheless starts a phase II trial with 600 participants. It hopes to launch a Phase III efficacy study in July to test whether the vaccine can prevent diseases in at-risk groups, such as health professionals and those with underlying medical problems.