Health authorities across the globe are looking at vaccines as the long-term solution to the disease which has wreaked havoc all over the world.

COVID-19 vaccine: A ray of hope! The first vaccine for COVID-19 to reach the first phase of clinical trial has been found to be safe and well-tolerated, and it can generate a response among humans that is immune to SARS-CoV-2, the coronavirus which causes COVID-19, a study published in The Lancet has found. In a statement, Lancet said that the trial, which was conducted among 108 healthy adults, has given a positive outcome within the first 28 days of the 6-month-long study. Further tests will ascertain if this immune response can effectively protect humans against SARS-CoV-2 infection.

Beijing Institute of Biotechnology’s Professor Wei Chen, who is conducting the study, has been quoted by Lancet as saying that the trial shows that a single dose of the vaccine called Ad5-nCov produced antibodies specific to the virus and T cells in 14 days. The Ad5-nCoV vaccine – an abbreviation of new adenovirus type 5 vectored COVID-19 vaccine – has therefore become a candidate to be studied further, Chen said. The professor, however, added that the results must be interpreted with caution, since the challenges in developing a vaccine against the COVID-19 are unprecedented, much like the virus itself.

Chen further stated that the ability of the trial vaccine to trigger an immune response does not translate to the fact that it would be able to protect humans from SARS-CoV-2. While the results are promising and give an indication towards the eventual development of a vaccine against the disease, there is a long walk till the vaccine is made available to all.

Health authorities across the globe are looking at vaccines as the long-term solution to the disease which has wreaked havoc all over the world. Therefore, over 100 vaccine candidates are under development globally at present.

According to Lancet, Ad5-nCoV is the first vaccine candidate to be tested among humans.

How does the vaccine work?

The vaccine uses a weakened common cold virus called adenovirus, which can readily infect human cells without causing any diseases. These weakened viruses deliver genetic material which codes for spike proteins of the SARS-CoV-2 to the cells, which then produce these proteins and travel to the lymph nodes. The immune system produces antibodies at these lymph nodes, and with the help of these cells, the system recognizes the spike protein of the SARS-CoV-2 and fights it.

Results of the study

The study checked how the vaccine generated immune response among humans depending on the dosage administered to the 108 healthy adults, who were aged between 18 and 60 years and did not have COVID-19. The study also assessed the safety of the vaccine in generating the response.

The 108 adults were enrolled from a site in Wuhan, China, and they were either administered an injection containing low dose (0.5 ml), medium dose (1 ml), or high dose (1.5 ml).

It was found that no serious adverse effect was reported for any dosage within the first 28 days, even as 83% each from low and medium dose groups and 75% from high dose groups reported at least one mild to moderate adverse effect within seven days of vaccination. The most common adverse effect was found to be mild pain at the site of injection of vaccine, and it was reported by 54% of the recipients. Apart from this, 46% recipients reported fever, 44% fatigue, 39% headache and 17% muscle pain.

The study further showed that within the first two weeks of vaccination, all dosage levels started showing some form of antibodies generation. Some of the recipients showed generation of antibodies which could bind to the coronavirus but not fight it, while some recipients showed antibodies which could detectably neutralise the virus.

The study further stated that within the first 28 days of the vaccination, most of the participants underwent a four-fold increase in binding antibodies, while half of the participants in each low and middle dose group and 75% participants in the high dose group showed antibodies which could neutralise the SARS-CoV-2.

Lancet study also stated that Ad5-nCoV vaccine also led to a rapid T cell response in most volunteers, and this response was greater in recipients of high and middle level dose, and the levels of T cells peaked at 14 days after vaccination.

Possible limitations in further experimentation

Authors of the study, however, stated that the production of T cells and antibodies, both could reduce if the recipient has high pre-existing immunity to the adenovirus type 5, which is the carrier of common cold. In the study, 44-56% of the participants, who had high pre-existing immunity to this carrier, showed less positive antibody and T cell response.

Professor Feng-Cai Zhu of China’s Jiangsu Provincial Center for Disease Control and Prevention was further quoted by Lancet statement as saying that a high pre-existing immunity to this virus could also negatively impact the immune response elicited by the vaccine.

The authors further stated that the study is limited due to the small sample size, relatively short duration, and non-randomized group, which can impact the ability of the study to pick up rarer adverse effects, or provide stronger evidence regarding the positive results of the vaccine.

All over the world, several studies are being conducted, with health experts all over the globe scrambling to develop a vaccine as soon as possible to contain the COVID-19 pandemic, which has so far infected over 51 lakh people globally, accounting for the death of over 3.3 lakh people.