How close are we to a Covid-19 vaccine? What is the testing process?
According to the World Health Organisations latest count, 13 experimental vaccines are being tested in humans and more than 120 others are in earlier stages of development.
China has six candidates undergoing human trials, the maximum.
The World Health Organisation’s (WHO) Solidarity Trial, the UK’s RECOVERY Trial and the US’s ‘Operation Warp Speed’ are three of the leading scientific efforts pivoting research in the battle against Covid-19.
What are the stages in development of a vaccine?
Firstly, a new vaccine candidate has to pass testing in animals, following which clinical trials kick in. Then, over three phases, the vaccine candidate’s safety and efficacy are tested as per protocols. A fourth stage involves collection and analysis of post-marketing data.
Pre-clinical tests: In this primary stage, scientists test the vaccine on animals such as mice or monkeys to see if it produces an immune response.
Phase I trials: This is the first step where the experimental vaccine is given to humans, usually between 20-80 subjects, to test safety and dosage and check whether it stimulates the immune system.
Phase II trials: In this stage, a larger group of several hundred individuals are enrolled for testing and they are split into groups age-wise such as children and elderly. The Phase II testing studies the candidate vaccine’s safety, immunogenicity, proposed doses, schedule of immunisations and method of delivery.
Phase III trials: Since certain side effects may not surface in the smaller groups of humans tested in earlier phases, the vaccine candidate is given to thousands of people in this stage. Here, the scientists check how many become infected compared with volunteers who receive a placebo. These trials can determine if the vaccine protects against the coronavirus.
Approval: After Phase III trials, the vaccine developer submits a license application to the regulatory authority in their respective country. The regulator then inspects the factory where the vaccine will be made and approves its labeling.
During a pandemic, a vaccine may receive emergency use authorisation before a formal green signal.
What types of vaccines are being developed?
With limited time in their hands, scientists are developing some vaccines from scratch and some from existing molecules developed for other diseases. What has aided the research is the fact that the novel coronavirus is from a family on which work is already being done worldwide after SARS and MERS.
Genetic vaccines: These are the vaccines that use the genes of the coronavirus (in the form of DNA or RNA) to provoke an immune response.
Viral vector vaccines: These vaccines use a virus to deliver coronavirus genes into cells and provoke an immune response. These viruses are weakened so they cannot cause disease.
Protein-based vaccines: These vaccines use a coronavirus protein or a protein fragment to provoke an immune response by mimicking the coronavirus’ outer coat.
Whole-virus vaccines: Such vaccines use a weakened or inactivated version of the virus. These vaccines are created by inactivating a pathogen, typically using heat or chemicals. This destroys the pathogen’s infectivity while retaining immunogenicity.
Which vaccines are the top contenders and have shown promise?
Even though most of the over 120 vaccines under development are undergoing Phase II clinical trials, only two of them are in combined Phase II/III trials.
1. Oxford-AstraZeneca vaccine -Phase II/III jointly developed by British-Swedish company AstraZeneca and the University of Oxford.
2. Moderna vaccine -Phase II)US firm Moderna Inc is developing a vaccine, part of US’ Operation Warp Speed
3. Pfizer-BNTECH vaccine -Phase II Pharmaceutical giant Pfizer, which is co-producing a Covid-19 vaccine with the help of German company BNTECH, has started the process of dosing patients.
4. Imperial College London vaccine -Phase II
5. Sinovac Biotech vaccine Phase II- Beijing-based
6. CanSino Biologics -Phase II Chinese vaccine company
7. Novavax vaccine -Phase II US biotechnology company
8. Sinopharm vaccine -Phase II China National Biotec Group (CNBG), known as Sinopharm
9. CureVac vaccine -Phase I German
10. Johnson & Johnson vaccine Phase I- American