In the midst of a global Covid-19 pandemic, the race is on to find a vaccine that reliably protects recipients against the newly discovered coronavirus. Teams of scientists around the world, backed by seemingly unlimited funds, are busily engaged in the search for an effective Covid-19 vaccine. But the production of a new vaccine, by itself, is not going to be enough. This race can only be won when a new vaccine is definitively proven to protect entire populations, subjected to mass vaccination, from the ravages of the virus.
As the race to deliver to a new vaccine intensifies, many competitive and nationalistic politicians are rushing to claim premature victory while many researchers are issuing optimistic press statements with overtly ambitious timelines. Furthermore, a new form of “vaccine nationalism” seems to be emerging, with some nation-states securing exclusive access to future supplies of Covid-19 vaccine through surreptitious pre-purchase agreements with vaccine manufacturers. The Covid-19 vaccine has even become a target for spies, leading to accusations by the UK, US and Canadian governments of Russian-sponsored cyber-espionage.
Closer to home, encouraging preliminary results of a Phase I/II trial of a new vaccine have been announced this month (July 2020) .This vaccine is being developed by the Oxford Vaccine Group, in partnership with the bio-pharmaceutical group AstraZeneca, at Oxford University’s Jenner Institute. Vaccination has been reported to generate sufficient levels of neutralising antibodies against Covid-19, and to stimulate the production of T cells (a special type of white blood cell which attack the virus) in all 543 vaccinated healthy adult recipients, aged between 18 and 55 years, in the UK. For the sake of comparison, a further 534 others have received a “control” inactive vaccine. Both groups of volunteers will be followed up for a minimum of 12 months to see whether they are protected against Covid-19 infection or not. Phase III trials of the Oxford University vaccine will now go ahead in the US and in several low- to middle-income countries, including Brazil and South Africa.
This takes us to the wider matter of immunity in general. People can be immunised against specific viruses naturally, by first being exposed to that virus, and then recovering from the ensuing viral infection. On the other hand, immunity can also be acquired artificially, either actively, by vaccination, or passively, by the administration of blood serum containing antibodies obtained from people who have successfully recovered from an infection. Active artificial immunity takes time to get established and also lasts longer, while passive immunity is short-lived and is thus restricted to providing rapid and temporary protection against the virus. Both approaches are currently being tested against Covid-19, in the form of vaccines for active immunisation and as the infusion of so-called “hyperimmune” serum for passive immunisation.
A viral vaccine can be developed from either live, but “attenuated” or weakened virus, killed virus, or from some critical viral component that the virus depends upon to successfully infect a human host cell. The Oxford University vaccine, for example, is based on the spike protein on the outer surface of Covid-19, which binds to ACE-2 receptors in susceptible human cells.
Any candidate vaccine has to be first developed in the laboratory. The selection of a suitable viral antigen (foreign protein) to form the basis of a vaccine is initially guided by cell-culture studies, tissue-culture studies, and animal experiments depending on the circumstances. Once considered suitable for testing on humans, each newly developed vaccine has to undergo a series of clinical trials. Phase I trials are initially used to assess vaccine safety. Phase II trials then establish the vaccine’s effective dose, method of delivery, and schedule for administration, while the monitoring of safety continues all the while. Finally, Phase III trials are conducted on much larger numbers of people, running into tens or hundreds of thousands, before the vaccine can be licensed for wider public use.
At the time of writing, more than 140 Covid-19 vaccines are being developed and many human Phase I and Phase II trials are taking place around the world, often in countries not directly involved in vaccine production. In this creative environment, many different approaches to vaccine development are emerging. For example, in the UK, another trial at Imperial College, London, is making use of a particularly innovative approach. The injection of a synthetic strand of self-amplifying Covid-19 RNA induces the production of spike protein in the human recipient, who then responds by producing protective antibodies.
Recent developments in India, which is a global leader in vaccine manufacture, are of particular interest. The Indian Council for Medical Research has announced that Covaxin, a Covid-19 vaccine being developed by Bharat Biotech in the city of Hyderabad, will be made available for public use by 15 August 2020 at the latest. This news has been met with some scepticism by the medical and scientific communities in the country. This rush to deliver a vaccine is by no means unique, as many politicians continue to rashly promise fast-tracked vaccines for speedy mass consumption.
Vaccine production is not a quick and easy process, and it seems most unlikely that any vaccine is likely to come onto the market any time this year. At a time when anti-vaccine sentiments are running high, it will also take more than simply demonstrating that a vaccine is safe and effective to ensure that enough people (as many as 70 percent of the population, and preferably more) are then vaccinated and thereby contribute to a state of protective herd immunity. Only time will tell. In the meantime, we can only hope that the vaccinologists can be relied upon to come up with the goods.
Ashis Banerjee