Given its low pricing and higher temperature storage, Oxford University’s COVID-19 vaccine candidate holds promise for India and is a more viable option than the Moderna, Pfizer or Sputnik V vaccines under development, say scientists while cautioning that the data presented is still preliminary.

There is plenty to be hopeful about and the Oxford AstraZeneca is a good option to begin with, but it is also important to remember the numbers are tentative and a full analysis is difficult, several scientists said on Tuesday.

On Monday, pharma major AstraZeneca announced that an interim analysis of clinical trials of its COVID-19 vaccine in the UK and Brazil showed it was 70 per cent effective on average.

The ChAdOx1 nCoV-2019 vaccine, being produced in collaboration with Oxford University, was found to be 70.4 per cent effective when combining data from two dosing regimens from Phase 3 clinical trials. However, in two different dose regimens, the vaccine’s efficacy was 90 per cent in one, and 62 per cent in the other.

These findings show that we have an effective vaccine that will save many lives. Excitingly, we’ve found that one of our dosing regimens may be around 90 per cent effective and if this dosing regimen is used, more people could be vaccinated with planned vaccine supply, explained Andrew Pollard, director of the Oxford Vaccine Group and chief investigator of the Oxford Vaccine Trial.

Tempering the excitement that the announcement created, virologist Upasana Ray said we should be happy but vigilant.

The interim results look promising but it would be difficult to analyse it fully without the full peer reviewed report, the senior scientist at Kolkata’s CSIR-IICB added.

There are knowledge gaps like why the lower dose gave better efficacy results or how long this vaccine can be stored in the refrigerator without negative temperature storage conditions. Also, the values might change after the completion of the entire trial, Ray told PTI.

However, compared to the other candidates, the Oxford vaccine appears to be a good option to start with, she said.

Three vaccine candidates have shown over 90 per cent efficiency over the last few days — Pfizer-BioNtech with 90 per cent efficacy in Phase 3 trial interim results, Sputnik V with 92 per cent and Moderna with 94.5 per cent.

The Pfizer-BioNtech vaccine needs extreme cold storage at minus 70 degrees Celsius and Sputnik V minus 20 degrees Celsius. Moderna can be kept in freezers for long-term storage though it doesn’t need the special facilities required for the Pfizer vaccine, the company said.

The Oxford vaccine can tolerate refrigeration for some period as opposed to the other successful candidates under Phase 3 like the mRNA vaccines which can only be stored at negative temperatures, Ray said.

Thus, the cold chain issue is slightly relaxed in case of the Oxford vaccine although this might not be true if the storage has to be made for a long term. As far as cost is concerned, if a lower prime dose works better, it will be more cost effective, she added.

Compared to other candidates under Phase 3 trials, the Oxford vaccine is in a better position in the Indian context although that doesn’t imply it is the best.

India is also waiting to see the results of the clinical trials of the indigenous inactivated vaccine candidate, COVAXIN and ZyCoV-D, Ray said.

Immunologist Satyajit Rath agreed that a vaccine candidate that can be used with India’s current public health vaccine cold chain is more promising than mRNA-based technologies that need very low to ultra low freezing temperatures.

The Oxford vaccine is made from a virus, which is a weakened version of a common cold virus (adenovirus) that has been genetically changed so it is impossible for it to grow in humans. The mRNA vaccines make use of the messenger ribonucleic acid (RNA) molecules that tell the body’s cells what proteins to build.

Rath added that Oxford AstraZeneca candidate’s numbers are subject to modification and said we should stop making too much of it at this stage .

What we should take away from the Oxford finding is that two different dosage regimens of their vaccine candidate are showing apparently very different levels of protection, Rath, from New Delhi’s National Institute of Immunology (NII), told PTI.

According to Rath, most SARS-CoV-2 vaccine candidate designs are likely to provide quite effective protection over the short term.

“Despite their reasonable statistical reliability, these and all the other recent data so far remain preliminary, and the actual numbers being bandied about all remain tentative and subject to modification, he cautioned.

Julian Tang, clinical virologist, Respiratory Sciences, at the University of Leicester in UK, echoed him and said the figures could change dramatically.

However, whilst the Pfizer and Moderna vaccine Phase 3 effectiveness estimates have included a diverse range of participants from different ethnic groups, the Oxford vaccine participants have been mainly drawn from a white Caucasian population in their early trials,” he said in a statement.

While it is tempting to compare efficacy between different vaccine candidates, Zania Stamataki, viral immunologist at the University of Birmingham in the UK said the early numbers will change as the vaccines are rolled out.

“These are early data designed to achieve approval,” Stamataki said.

Codenamed AZD1222, the Oxford vaccine is comparatively cheaper and easier to store.

According to Zoltan Kis, research associate at the Future Vaccine Manufacturing Hub, Imperial College, London, AZD1222 has the advantage that it can be distributed and stored at temperatures between 2-8 degrees Celsius.

In addition, AZD1222 is available at a lower purchase price than the mRNA vaccines which are currently in late-phase clinical development. This makes the AZD1222 vaccine candidate a more viable option for low- and middle-income countries, Kis said.

Stephen Evans, professor of Pharmacoepidemiology, London School of Hygiene & Tropical Medicine, concurred.

Evans termed the interim results of the Oxford vaccine really good news, adding the vaccine can be stored in ordinary refrigerators, which helps in high-income countries but is of enormous importance for low-income countries.

Pricing is another big factor.

Last week, Adar Poonawalla, CEO of Serum Institute of India (SII), which is manufacturing the vaccine and conducting clinical trials, said the Oxford COVID-19 vaccine should be available for healthcare workers, elderly people by around February 2021 and by April for general public. It would be priced at a maximum of Rs. 1,000 for two necessary doses.

A single dose (two are recommended at this stage) will cost up to Rs 1,000 if purchased from the pharmacy, but the government will buy 90 per cent of the supply at Rs 250 per dose, he explained on Monday in an interview with NDTV.

Moderna will reportedly charge governments between USD 25 (Rs 1,854) and $37 (Rs 2,744) per dose, while Pfizer will price its vaccine at USD 20 (Rs 1,480) per dose for its vaccine.

Rath noted that the details of agreements, commitments and promises that SII may have made to Astra-Zeneca and to the government of India are not in the public domain.

“It is hard to put a great deal of reliance on the supply schedule and pricing from SII to the government of India for the eventual Astra-Zeneca vaccine, the immunologist said.