Covid-19 vaccine, dreams coming true?
People obsessed with the 'first successful vaccine' while developing an efficacious vaccine against Covid-19 are now in various stages of the clinical trials pipeline. Already Pfizer Bio Ntech said their vaccine against Covid-19 efficacy is 90%; Moderna said their vaccines have an efficacy rate of 95% , the Russian team, Gamaleya Research Institute, claimed that their vaccine Sputnik V had an efficacy rate of 92%. Also, the University of Oxford and AstraZeneca has announced that their vaccine efficacy rate was between 62-90%, with an average efficacy rate of 70%. Regulators need at least a 50% efficacy rate for approval of Covid-19 vaccine for use.
What is the efficacy rate?
If any Covid-19 vaccine manufacturers claim the efficacy rate is 90%, which means any person who has not previously been infected with the virus when they receive the vaccine, will be protected from the virus, on an average 90 of them. However, they might develop some symptoms. In the real world this efficacy rate may be influenced by many factors, for instance, whether the vaccine was stored at the correct temparature, ( Pfizer vaccine needs to be stored in -70 C.Moderna vaccine requires -20 C for storation) individuals immune system response, how quickly the virus is spreading etc. Frankly speaking, in the real world vaccine efficacy is lower than manufacturers claimed efficacy rate.
Oxford University and AstraZeneca Vaccine: People around the world are passionately waiting to see the successful completion of this vaccine trial because it has entered the vaccine phase III efficacy trial before other frontrunners who are doing clinical trials to develop vaccines.
Their published data showed the efficacy level varies 62% to 90% from the two different dosing regimens. Trial participants who have received 2 full doses of the vaccine showed a 62% efficacy level, interestingly, volunteers who have received first, half a dose and second, a full dose had an efficacy level of 90% efficacy. The more effective half dose and full dose results were based on released data of 2,741 trial participants and less efficacious two full dose recipient 8,895 volunteers.
Scientists around the world are divided about the published data on the lower first dose which had a better efficacy. Katie Ewer, an immunologist, Oxford university Jenner Institute of Vaccine argued that a lower first dose may work better to stimulate the subset of immune cells called T cells which help to produce antibodies. Professor Sarah Gilbert who is leading the vaccine trial at the Oxford University also believes the same. Professor James Wilson from the University of Philadelphia, who pioneered developing vaccine from adenovirus, also believes giving half the first dose may stimulate the immune system better. Hildegund Ertl, a viral immunologist at the Wistar said: lower first dose leads more quickly to the establishment of memory cells that are triggered by a second full dose.
Professor Helen Fletcher, an immunologist, at the London School of Hygiene and Tropical Medicine would like to wait to see the full data of phase III trials is released but he thinks it is still possible that lower initial dose could result in better vaccine efficacy. Dr Charlie Weller, Head of Vaccine at 'Wellcome' said: it is important to take a step back and remember that these are still many answered questions. We need to be careful before drawing the conclusion, and we must wait for the trial to finish and trialled data to be independently and rigorously assessed. Professor Peter Openshaw at the Imperial College London said, "We have to wait for the full data and to see how the regulators view the results of the phase III trials. The US and European regulators might possibly take a different view. All we have to go on is a limited data release. The protection from the Oxford AstraZeneca vaccine may be less than that from the RNA vaccine, but we need to wait and see."
Professor Chris Whittey, Chief Medical Officer, UK refused to back the vaccine when asked at Downing Street press conference about the controversy surrounding the data released by Oxford AstraZeneca vaccine. He said judgement about the vaccine's efficacy and safety should be 'left in the hands' of the UK's drug watchdog, which will decide whether the jab is safe enough to dish out to millions of Britons in a matter of days. He added, "The simple answer to this there is always scientific debate about virtually everything. The key thing from our point of view is to leave this in the hands of the regulator, the excellent Medicine and Healthcare products Regulatory Agency (MHRA)."
Imperial College London Vaccine
The Imperial College vaccine development team has started developing a covid-19 vaccine in January this year led by Professor Robin Shattock ,this team is developing new self-amplifying RNA(saRNA) technology. After successful phase I and II human trials,it now started phase III human trials, recently collaborated with Indonesian government to trial in Indonesia in addition to the UK. If phase III clinical trial is successful it would revolutionise vaccine development.
Normally it takes 5-8 years to develop a vaccine, but successful Covid-19 coronavirus vaccine trial by Imperial team means scientist could develop a successful vaccine within 8 weeks. Professor Robin Suttock said, "Everybody is very obsessed with the 'first' vaccine but the first may not be the best vaccine."
Sinovac Biotech, Chinese vaccine entered in phase III human trial. On November 17, British Medical Journal the Lancet mentioned volunteers participating in the trial developed a lower level of antibodies than those present in recovered coronavirus patients. Judgement would be fair when full data is due to be released next month.
Another valid question to ask - will the claimed successful vaccine stop this pandemic? The answer to this question, so far successful vaccine Pfizer and Moderna vaccine would be able to stop people developing the disease, only Oxford and AstraZeneca vaccine data shows their vaccine may stop transmission of the disease. Partly released data on 23 November showed 131 volunteers developed Covid-19 cases among over 11000 volunteers participated in the trial in the UK and Brazil, up to 4 November.
The UK probably would be the first western country to approve a Covid-19 vaccine within days, first vaccine could take place from 7 December 2020, for any developing country possibly Oxford Astrazeneca vaccine would be more accessible because of the advantage of it could be stored at regular fridge temperature. At least 50% efficacy is efficacy is required by the regulatory bodies for approval of human use of vaccine. Oxford-AstraZeneca vaccine phase III trial efficacy is 62%-90%. Decision of quick access to Oxford AstraZeneca now depends on regulatory bodies and governments around the world.
The writer is clinical lecturer, Faculty of Medicine, Imperial College London