Researchers report ‘extremely encouraging’ COVID-19 vaccine data
Two studies published on the same day by The Lancet reported encouraging data on two COVID-19 vaccine candidates, one being developed at Oxford University and the other in Wuhan, China.
The Oxford vaccine, which is being developed in a partnership with AstraZeneca, induced strong antibody and T cell immune responses with an acceptable safety profile in a phase 1/2 trial, researchers reported. A phase 2 trial evaluating the vaccine being developed in China also showed that it was safe and induced an immune response in most recipients following a single immunization, according to the study.
In a related editorial, Naor Bar-Zeev, PhD, and William John Moss, MD, both of Johns Hopkins Bloomberg School of Public Health, noted that almost 200 COVID-19 vaccine candidates are currently in development. The new studies were published less than a week after the release of promising phase 1 data from the first COVID-19 vaccine given to people in the United States.
“Dystopian realities generate utopian visions,” Bar-Zeev and Moss wrote. “Science reveals itself to the world in real time in all its glorious uncertainties, but also in all its careful, hard-won, and real achievements.”
“These trial reports are hugely anticipated,” they wrote. “The results of both studies augur well for phase 3 trials, where the vaccines must be tested on much larger populations of participants to assess their efficacy and safety. Overall, the results of both trials are broadly similar and promising, notwithstanding differences in the vector, in the geographical locations of the populations studied, and the neutralization assays used.”
‘Very positive news’
Andrew J. Pollard, MBBS, PhD, FMedSci, and colleagues from the Oxford COVID Vaccine Trial Group conducted a single-blind, randomized controlled trial of a candidate vaccine at five sites in the United Kingdom. They randomly assigned healthy adults aged between 18 and 55 years with no history of the SARS-CoV-2 infection or any COVID-19 symptoms to receive either a chimpanzee adenovirus-vectored vaccine (ChAdOx1 nCoV-19) expressing the SARS-CoV-2 spike protein or a meningococcal conjugate vaccine (MenACWY).
Of 1,077 participants, 543 received ChAdOx1 nCoV-19 and 534 patients received the MenACWY vaccine.
Among participants who received the candidate vaccine, “antibodies against SARS-CoV-2 spike protein peaked by day 28 (median 157 ELISA units [EU], IQR 96–317; n=127) and remained elevated to day 56 (119 EU, 70–203; n=43) in participants who received only one dose, and increased to a median of 639 EU (360–792) at day 56 in the 10 participants who received a booster dose,” Pollard and colleagues reported.
According to the researchers, T-cell responses peaked on day 14 (median 856 spot-forming cells per million peripheral blood mononuclear cells, interquartile range 493 to 1,802; n = 43).
Pollard and colleagues assessed safety after 28 days. Local and systemic reactions to ChAdOx1 nCoV-19 were common, and many were reduced using prophylactic paracetamol, they said. Reactions included pain, feeling feverish, chills, muscle aches, headaches and malaise. No serious adverse events occurred for any participant.
The authors said the results support large-scale evaluation of the vaccine in an ongoing phase 3 trial. Lancet Editor-in-Chief Richard Horton, FRCP, FMedSci, tweeted that the results were “extremely encouraging.”
“This is very positive news,” United Kingdom Prime Minister Boris Johnson wrote on Twitter. “A huge well done to our brilliant, world-leading scientists and researchers at the University of Oxford. There are no guarantees, we’re not there yet and further trials will be necessary — but this is an important step in the right direction.”
Ad5-vectored COVID-19 vaccine
In the second study, researchers reported that a non-replicating adenovirus type-5 (Ad5)-vectored COVID-19 vaccine (CanSino Biologics) “induced significant immune responses in the majority of recipients after a single immunization,” the researchers wrote.
Healthy adults aged at least 18 years who were HIV negative and free of SARS-CoV-2 were eligible to participate in the study. Participants received either the vaccine at a dose of 1 x 1011 particles/mL, a dose of 5 x 1010 particles/mL or placebo.
According to the study, the primary endpoints for immunogenicity were the geometric mean titers (GMTs) of specific ELISA antibody responses to the receptor-binding domain (RBD) and neutralization of antibody responses after 28 days. For safety, the researchers looked for any adverse reactions occurring by day 14.
Among the 508 participants, 50% were male. Participants had a mean age of 39.7 years. In total, 253 received a dose of 1 x 1011 particles/mL, 129 received a dose of 5 x 1010 particles/mL and 126 received a placebo.
The RBD-specific ELISA antibodies peaked at 656.5 (95% CI, 575.2-749.2) for the group receiving a dose of 1 x 1011 particles/mL and 571 (95% CI, 467.6-697.3) for the group receiving a dose of 5 x 1010 particles/mL. Almost all participants in the non-placebo arms — 96% (95% CI, 93-98) in the first group and 97% (95% CI, 92-99) in the second — showed seroconversion at day 28.
Both vaccines induced “significant” neutralizing antibody responses to SARS-CoV-2 and researchers observed specific interferon gamma enzyme-linked responses after vaccination in 227 of 253 participants in the 1 x 1011 group (90%, 95% CI 85-93) and 113 of 129 in the 5 x 1010 group (88%, 95% CI 81-92).
According to the researchers, solicited adverse reactions were reported by 183 of 253 participants in the 1 x 1011 group (72%), and 96 of 129 patients in the 5 x 1010 group (74%). Severe adverse reactions were reported in 24 participants in the 1 x 1011 group and in one participant in the 5 x 1010 group. No serious adverse reactions were reported.
- Bar-Zeev N, Moss WJ. Lancet. 2020;doi:10.s0140-6736(20)31611-1.
- Folegatti PM, et al. Lancet. 2020;doi:10.1016/S0140-6736(20)31604-4.
- Jackson LA, et al. N Engl J Med. 2020;doi:10.1056/NEJMoa2022483.
- Zhu FC, et al. Lancet. 2020;doi:10.1016/S0140-6736(20)31605-6.