Oxford-AstraZeneca’s COVID-19 Vaccine Demonstrates Strong Immune Response in the Elderly
November 19, 2020 – With more than 55 million people infected, and over 1.3 million deaths, the coronavirus pandemic has ravaged the world unlike any other in recent memory. The scientific community has been working tirelessly, and their hard work has already resulted in multiple vaccine candidates, including Moderna’s and Pfizer, with BioNTech’s showing promising results. Today, AstraZeneca published encouraging data from their Phase 2 trial that evaluated its vaccine candidate, AZD1222. Results show that the vaccine elicits a strong immune response in the elderly.
Phase 2 Clinical Trial
About 560 healthy volunteers were enrolled in the trial to test the efficacy and immunogenicity of AZD1222. Among them, 320 in the age group of 18-69 years and 200 aged over 70 years were given the vaccine, while the remaining 40 received placebo. Interestingly, the study demonstrated that the immunogenicity of the vaccine was similar across all age-groups. Antibodies against the SARS-CoV-2 virus were seen in the subjects 28 days post-vaccination, and a booster dose further increased their levels. Besides, there was an increased T-cell immune response post-vaccination.
“The robust antibody and T-cell responses were seen in older people in our study are encouraging. 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,” said Maheshi Ramasamy, a consultant and co-lead investigator at the Oxford Vaccine Group. “We’re still waiting to get to the point where we can do the analysis to just work out how well the vaccine can protect people, and we’re getting ever closer to that. We are optimistic that we’ll be able to do that before Christmas, and obviously, we’ll share that with you as soon as we can at that point.”
This data is encouraging, given that vaccines usually produce weaker responses in adults, and the COVID-19 morbidity rate is higher in the older population. However, the study has several limitations, the main being that older adults may not be a good representative of the entire population. The older population’s median age in the study is 73-74 years, which is lower than the people who will be vaccinated first in the UK. Further, these individuals were healthier than a normal senior without any comorbidity.
Thus, the Phase 3 trial, which would include patients with comorbidity, will give us more insights into the vaccine’s safety and efficacy. It is to be noted here, although no major vaccination-related adverse effects were observed in Phase 2, the Phase 3 trial had to be delayed due to safety concerns.
A Sprint Towards the Finish Line
AstraZeneca and Oxford’s collaboration, AZD122, started as a frontrunner in the race to obtain a COVID-19 vaccine. However, due to safety concerns, Pfizer’s and Moderna’s candidates have inched ahead. In the last 10-days, both these companies have released data showing more than 94% efficacy of their respective mRNA-based vaccines. Pfizer further announced that they are filing for emergency approval in the next few days. If approved, the vaccine will be available for frontline workers from December.
Further, Chinese drug maker Sinopharm announced that 1 million people had received their vaccine without safety concerns. China has already allowed two vaccines from Sinopharm and one from Sinovac to be injected into frontline workers without a Phase 3 trial. Russian vaccine, Sputnik V has also been given to frontline workers without a Phase 3 trial. With AstraZeneca scheduled to release Phase 3 data around Christmas, they may be a bit behind in the vaccine race. However, that could change if the safety and efficacy data could trump the other candidates.
By T. Chakraborty, Ph.D.
Editor: Rajaneesh K. Gopinath, Ph.D.
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