E-Paper
A year of trials: Controversies, pitfalls AstraZeneca-Oxford Covid-19 vaccine faced
Researchers have stressed time and again that regardless of the dosing regime, none of the trial participants developed severe coronavirus symptoms or had to go into hospital with the disease after having just one dose of the vaccine.
Researchers at the University of Oxford built their vaccine using adenovirus, a virus that causes cold in chimpanzees. They genetically altered the virus to make it carry a gene for a coronavirus protein, which researchers said would train a person’s immune system to recognize the real coronavirus. Adenovirus-based vaccines are not an anomaly. Russia’s Sputnik-V and a Chinese vaccine have also used similar technology, but both vaccines have not published credible results or submitted their findings to be peer-reviewed. Hence, the efficiency of these are unknown. Adenovirus vaccines have also been patented before for Ebola by pharma giant Johnson and Johnson.
Why was its efficacy being doubted?
In the spring of 2020, AstraZeneca and Oxford started running clinical trials in Britain and later in other countries. The first round of trials showed volunteers were producing antibodies and the vaccine was deemed to be on the right part. On November 23, however, the team behind the vaccine reported that due to an error, two sets of volunteers had received two types of doses. The group which had received two full doses of the vaccine developed only 62% efficacy, whereas the group that had received the accidental dose of one half shot followed by the full shot showed 90% efficacy. Reuters reported that researchers were baffled when the usual side effects of fatigue, arm aches, and headaches were much milder than expected. On checking, they found out that the group had been administered only half the initial dose of the vaccine. No one knows the reason behind this anomaly and the researchers have attributed it to a lucky coincidence.
What impact did the dosing error have?
The main issue seems to be with the limited size of the group which received half a dose followed by a full dose. It was considerably smaller than the group given two full doses and did not include participants over the age of 55. This controversy led AstraZeneca to announce in November a new global trial of the vaccine with the half dose/full dose regime.
However, researchers have stressed time and again that regardless of the dosing regime, none of the trial participants developed severe coronavirus symptoms or had to go into hospital with the disease after having just one dose of the vaccine, and both older and younger participants showed a similar immune response to the jab. Fewer than 2,800 volunteers got the initial half dose, out of the total 23,000 participants whose results were reported. That’s a pretty small specimen to base efficacy results on.
In the Phase 3 trials, some neurological issues also cropped up in volunteers in the US and India. The US Food and Drug Administration did not tie the vaccine directly with the issue but the developer was asked to exercise caution. In its final report too, AstraZeneca and Oxford said that no serious safety issues were caused by the vaccine in the trial group
How does it fare in comparison with other vaccines?
The Oxford vaccine does not have to be stored and transported at a super cold temperature like the Pfizer/BioNTech one, which needs -70C. It can be easily stored in regular medical refrigerators at 2C-8C for up to five days, making it a more viable and less cost-intensive option for tropical countries. Moreover, at about $3-4 per shot, the Oxford vaccine is much cheaper than the Pfizer vaccine, which is said to be priced around $20.
