Oxford University and AstraZeneca's coronavirus vaccine candidate was safe, boosted an immune response, and was better tolerated among older adults, according to phase 2 clinical trial data.

Researchers recruited 560 participants, 240 of which were aged 70 or older. The results were published in the peer-reviewed journal, The Lancet, on Thursday.

If the boosted immune response correlates to protection against the virus, researchers say the “findings are encouraging” because older adults are at higher risk of more serious outcomes after infection. The ongoing phase 3 trial will assess the vaccine's effectiveness.


Researchers said the vaccine candidate invoked a so-called “T-cell response” 14 days after vaccination, with an antibody response 28 days later. (iStock)

The team found that younger participants experienced side effects like pain at the vaccine's injection site, fever and muscle ache more often than older adults. More specifically, after two doses, 88% of those aged 18 to 55 had so-called “local reactions,” (redness and swelling at injection site) whereas 61% of participants over 70 experienced these reactions. 

The team said the latest findings upheld research from an earlier phase.

Also, by October 26, there were 13 serious adverse events, though researchers said “none of which are considered related to either study vaccine as assessed by the investigators.” Earlier, reports arose of one volunteer’s death in Brazil during the phase 3 trial, and researchers said serious adverse reactions would be described in a future report.

The phase 3 trial was briefly put on pause before it restarted late last month. 

A top scientist at the World Health Organization (WHO), Dr. Soumya Swaminathan, had said the pause in the study was a “good wake-up call,” given “ups and downs in research.”

“Independent assessments have led to the recommendation that the trial is safe to continue,” study authors wrote.


Finally, researchers said the vaccine invoked a so-called “T-cell response” 14 days after vaccination, with an antibody response 28 days later.

“T cells are lymphocytes which are parts of white blood cell that help fight various infections,” Dr. Adi Shah, infectious disease expert at Mayo Clinic, uninvolved with the AstraZeneca trial, previously told Fox News. “Studies suggest T cells play a large role in immune response to the coronavirus, [and] what kind of role they play [is] being investigated.” 

The Oxford-AstraZeneca team said the phase 2 trial had its limitations, including how participants aged over 70 had few underlying health conditions which “might not be representative of the general older population,” though ongoing late-stage trials are assessing the vaccine in older adults with more comorbidities.