Phase-1 trial: Adenovirus COVID-19 vaccine found safe, induces immune responses

Henrietta Strickland
May 24, 2020

The Cansino Ad5 is a non-replicating vector that expresses the full-length spike protein of SARS-CoV-2, the causative agent of COVID-19.

While pharmaceutical companies have worked on developing and producing vaccines on a large scale since the middle of the last century - again, the polio vaccine serves as a benchmark - it is still not a simple, quick or infallible task to produce it in the quantities needed to vaccinate - literally - the entire planet.

"Our study provided a new vaccine platform simulating coronavirus surface protein and internal nucleic acids, therefore, combining features of inactivated vaccines and mRNA vaccines", the researchers added.

Participants were enrolled from one site in Wuhan, China, and assigned to receive either a single intramuscular injection of the new vaccine at a low dose of 5 × 1010 viral particles per 0.5 milliliters, a middle dose of 1×1011 viral particles per 1.0 ml. or a high dose of 1.5 x 1011 viral particles per 1.5 ml. By 28 days, almost all participants had developed antibodies that bound to SARS-CoV-2 (but don't necessarily attack the virus), and about half of the participants in the low- and middle- dose groups and three-quarters of participants in the high-dose group developed "neutralizing antibodies", which bind to and disable the virus to prevent it from infecting cells. Within two weeks of vaccination, the study noted that all dose levels of the vaccine triggered some level of immune response.

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

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 people in the low-dose group, two in the middle-dose and five in the high-dose group had a grade 3 high fever with an ancillary temperature (checked in armpits) above 38.5°C.

No clinically significant abnormal changes in laboratory values were seen.

One person in the high dose group experienced severe fatigue, breathing difficulties and muscle pain. However, these adverse reactions persisted for less than 48 hours. In studies of lungs from seven patients who died of COVID-19, researchers found damage to tiny air sacs in the lung called alveoli.

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Authors noted, "However, 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)-in the study, 44%-56% of participants in the trial had high pre-existing immunity to adenovirus type 5 and had a less positive antibody and T-cell response to the vaccine".

All nine animals showed little to no symptoms after re-challenge and exhibited immune responses that protected against the second infection (given at the same doses as the first).

The trial did not involve randomisation of participants and did not have a control arm.

The follow-up duration was really short.

Only 16% of people in the study were above 50 years and none above 60.

Most of the people dosed with the vaccine had immune responses, although their levels of antibodies thought to neutralize the virus were relatively low.

For more information, read our article on Coronavirus vaccine candidates.

This article has been adapted from its original source. At myUpchar, researchers and journalists work with doctors to bring you information on all things health.

Other reports by Click Lancashire

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