China's Covid-19 vaccine shows promising results in early trials

Vials of CanSino’s non-replicating Ad5 vectored COVID-19 vaccine

Vials of CanSino’s non-replicating Ad5 vectored COVID-19 vaccine

Volunteers were enrolled from one site in Wuhan, China, and assigned to receive either a single intramuscular injection of the new Ad5 vaccine at a low dose (5 × 1010 viral particles/0·5ml, 36 adults), middle dose (1×1011 viral particles/1.0ml, 36 adults), or high dose (1.5 x 1011 viral particles/1.5ml, 36 adults).

The study was non-randomised and did not have any controls. The results are based on short duration of follow-up. Fever (46%), fatigue (44%), and headache (39%) were the most common systemic adverse events.

In an observational study of more than 96,000 COVID-19 patients at 671 hospitals on six continents, the malaria drug hydroxychloroquine was tied to an increased risk of death, researchers reported on Friday.

Nine Rhesus Macaque monkeys - similar to this one - were given a trial coronavirus vaccine in a USA study that found they were ultimately immunised or resisted re-infection. These reactions occurred within a day after vaccination and did not persist for more than two days.

The vaccine candidate was well tolerated at all doses with no serious adverse events reported within 28 days of vaccination.

CBS News reports that they have optimistic results after a COVID-19 vaccine trial with rhesus monkeys. While significant reductions of the virus were observed after just a few minutes of simulated sunlight, the risk of exposure from contact with surfaces may not be fully eliminated, the researchers cautioned in the Journal of Infectious Diseases.

Cai Yujia, one of the researchers, recently told the South China Morning Post that if the team finds a partner to help them develop the vaccine, they will need three or four additional months of pre-clinical research before human trials can be conducted.

Respiratory Droplets, Not Surfaces, Are The Main Way COVID-19 Is Spread
This takes us back to a similar vocabulary as on May 10. "COVID-19 spreads mainly through close contact from person to person". But it's more important to avoid indoor gatherings, where an asymptomatic person could easily spread the virus, he said.

The researchers tested three doses and said the highest dose seemed to be the most effective. Mean titer for neutralising antibody in the high-dose group was noted to be 34.0, while it stood at 16.2 in the middle and 14.5 in the low-dose group. Meanwhile, 18 (50%) participants in the low-dose group, 18 (50%) in the middle-dose group, and 27 (75%) in the high-dose group showed neutralising antibodies against the virus.

A majority of participants also produced virus-fighting T cells two weeks after taking the vaccine, which were also greatest at the higher dose levels.

Furthermore, after 28 days, the majority of recipients showed either a positive T cell response or had detectable neutralizing antibodies against SARS-CoV-2 (low-dose group 28/36, 78%; medium-dose group 33/36, 92%; high-dose group 36/36, 100%).

The pre-existing immunity to adenovirus type-5 vector used in the vaccine, regardless of the vaccine doses, could reduce the immune responses (both neutralising antibodies and T-cell response) to the virus and also lower the peak of the responses, particularly for neutralising antibodies immunity.

However, they noted that both the antibody and T-cell response could be reduced by high pre-existing immunity to adenovirus type 5 - the common cold virus vector/carrier.

The trial did not cause any weight loss in the mice, which means the vaccine is likely not toxic to the animals.

In a separate study that included numerous same researchers, titled "DNA vaccine protection against SARS-CoV-2 in rhesus macaques", the team developed a series of DNA vaccine candidates expressing different forms of the SARS-CoV-2 Spike (S) protein and evaluated them in 35 rhesus macaques (25 adult rhesus macaques with the investigational vaccines and 10 animals received a sham control).

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