The first COVID-19 vaccine to reach Phase 1 clinical trials has been found to be safe, effective and without severe adverse effects. The results of the trial, held at the Beijing Institute of Biotechnology in China, have been published in The Lancet.
The next step is for the vaccine to enter a randomized, double-blinded, placebo-controlled Phase 2 trial, which has already been initiated in Wuhan, to ensure the positive results can be replicated among a larger sample size.
The Beijing trial evaluated the effect of a single dose of the new adenovirus type 5 vectored COVID-19 (Ad5-nCoV) vaccine. This vaccine uses a weakened common cold virus (adenovirus) to deliver genetic material that codes for the SARS-CoV-2 spike protein to the cells. These cells then produce the spike protein, and travel to the lymph nodes where the immune system creates antibodies that will recognize that spike protein and fight off SARS-CoV-2. The researchers specifically designed the vaccine to generate a two-prong immune response—the development of virus-specific antibodies as well as T-cells.
The trial assessed the safety and effectiveness of three dosage amounts (low, medium and high) of Ad5-nCoV on 108 healthy adults between the ages of 18 and 60. In general, the high dose revealed a greater immune response than the middle and low doses; although, all doses did trigger some level of immune response within two weeks of vaccination.
In 14 days, all three doses triggered an immune response in the form of binding antibodies—those that bind to the coronavirus but do not necessarily attack it. The high dose group saw 61% of participants form antibodies, while 50% of those in the middle dose group did, and 44% in the low dose group. After 28 days, most participants had a 4x increase in binding antibodies—97% in the low-dose group; 94% in the middle-dose group; and 100% in the high-dose group.
Importantly, the Ad5-nCoV vaccine also stimulated a rapid T cell response in the majority of participants, which was greater in those given the higher (97%) and middle (97%) doses of vaccine, than the low dose (83%). All levels, regardless of dosage, peaking at 14 days following vaccination.
While no serious adverse effects were recorded, the authors did note that about half of the participants had high pre-existing immunity to adenovirus type 5, and therefore had a less positive antibody and T-cell response.
“These results should be interpreted cautiously,” said Wei Chen, professor at the Beijing Institute of Biotechnology, and lead author of the study. “The challenges in the development of a COVD-19 vaccine are unprecedented, and the ability to trigger these immune responses does not necessarily indicate that the vaccine will protect humans from COVID-19. This result shows a promising vision for the development of COVID-19 vaccines, but we are still a long way from this vaccine being available to all.”
The Phase 2 trial in Wuhan will determine if the study results can be replicated, and if there are any adverse effects up to 6 months after vaccination. The study cohort will include 500 healthy adults—250 volunteers given a middle dose, 125 given a low dose, and 125 given a placebo as a control—and will include participants over 60 years old, an important target population.
Worldwide, there are more than 100 COVID-19 candidate vaccines in development. Until a vaccine (or drug) is proven safe and effective, COVID-19 is likely to stick around. Some experts predict a second wave as quarantine restrictions lift or school resumes after the summer, while others say we may need to continue the practice of social distancing every few weeks. A vaccine is seen as the only long-term solution to controlling COVID-19 and reestablishing “normal”—and scientists in Bejing may have just provided the first step.