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Oxford’s COVID-19 Vaccine is Safe and Produces an Immune Response in Older Adults, Encouraging Phase 2 Data Shows

Early trial results published in The Lancet suggest the University of Oxford and AstraZeneca's COVID-19 vaccine produces an immune response and is safe in older adults.

November turned out to be the month of good Covid-19 vaccine news. After the promising interim results of the Pfizer and Moderna Phase 3 trials, the results of the Oxford Vaccine Phase 2 trial have been published.

The Oxford coronavirus vaccine shows a strong immune response in adults in their 60s and 70s, raising hopes that it can protect age groups most at risk from the virus.

This is important because older adults are more likely to develop severe cases of infection from the virus, and some vaccines aren’t as effective on them.

The Oxford Vaccine (ChAdOx1 nCoV-19) was administered to 560 people in two standard doses. The team reports in the journal Lancet that 14 days after the booster dose 208 out of the 209 participants that received both doses had neutralizing antibodies.

They are also testing whether the vaccine stops people developing Covid-19 in larger, phase three trials.

Early results from this crucial stage are expected in the coming weeks.

Three vaccines – Pfizer-BioNTech, Sputnik and Moderna – have already reported good preliminary data from phase three trials, with one suggesting 94% of over-65s could be protected from Covid-19.

The Oxford data is from an earlier stage, which tests the safety of the vaccine and the body’s response to it, but in the long run it’s likely this vaccine could be easier to roll out because it doesn’t need to be stored at very cold temperatures.

Side Effects

Another excellent piece of news is that the vaccine is well tolerated with side effects only around the injection site and only lasting for a short period of time. And it turns out that older adults are less likely to have local reactions where they got the injection and symptoms on the day of vaccination compared to younger people.

“Older adults are a priority group for COVID-19 vaccination, because they are at increased risk of severe disease, but we know that they tend to have poorer vaccine responses,” Dr Maheshi Ramasamy, Investigator at the Oxford Vaccine Group and Consultant Physician, explained.

“We were pleased to see that our vaccine was not only well tolerated in older adults; it also stimulated similar immune responses to those seen in younger volunteers. The next step will be to see if this translates into protection from the disease itself.”

ChAdOx1 nCov-2019 vaccine is currently undergoing its Phase 3 trial with 40,051 participants currently enrolled. The first interim results of efficacy readings for this trial are expected to be reported in the coming weeks. The vaccine uses a chimpanzee adenovirus which has been genetically modified to have the same external spike proteins as SARS-CoV-2, the virus behind Covid-19. This adenovirus doesn’t infect humans but its presence trains our immune system to recognize these spike proteins as a danger.

‘Protect Most Vulnerable’

Dr Maheshi Ramasamy, an investigator at the Oxford Vaccine Group, said: “The next step will be to see if this translates into protection from the disease itself.”

Two weeks after the second dose, more than 99% of participants had neutralising antibody responses. These included people of all ages.

The T-cell response – another measure of how well the immune system responds – peaked two weeks after the first dose of the vaccine, regardless of age.

“The robust antibody and T-cell responses seen in older people in our study are encouraging,” Dr Ramasamy said.

“The populations at greatest risk of serious Covid-19 disease include people with existing health conditions and older adults. We hope that this means our vaccine will help to protect some of the most vulnerable people in society, but further research will be needed before we can be sure.”

Older adults were also less likely to experience side-effects, which were usually mild.

And there were no serious safety issues relating to the vaccine, called ChAdOx1 nCov-2019.

Volunteers in the trial were put into groups and given one or two doses of the vaccine or a dummy jab. The reaction of their immune systems was assessed on the day they got the jab, then one, two and four weeks after both doses.

The Oxford vaccine is made from a weakened version of a common cold virus (known as an adenovirus) from chimpanzees that has been modified so it cannot grow in humans.

Work began on the vaccine in January and it was developed in under three months, starting human trials – the first in Europe – in April in Oxford.

Phase three trials of the vaccine, which look at how effective it is at protecting people against the Covid-19, started at the end of August and are still continuing.

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