Global race for COVID-19 vaccine gains momentum

Elvira Manzano
04 Aug 2020

The global race for a COVID-19 vaccine moves at an unprecedented speed, buoyed by public pressure and geopolitical crosscurrents that were punctuated by deaths and infections around the world.

Seven vaccine candidates already entered human clinical testing. Nearly 70 more are in the pipeline.

One of the frontrunners, ChAdOx1 nCoV-19, a vaccine the University of Oxford in UK is developing with AstraZeneca, showed promising preliminary results in the phase 1/2 clinical trial.

ChAdOx1 nCoV-19, also known as AZD1222 vaccine, was demonstrated to be safe, with only a few side effects, and induced strong immune responses. It provoked a T-cell response peaking at 14 days post-vaccination, and an antibody response within 28 days. [Lancet 2020;doi:10.1016/S0140-6736(20)31604-4]

The vaccine was tested vs a meningococcal conjugate vaccine in 1,077 healthy adults (age 18–55 years) from 5 UK hospitals, who had no history of COVID-19. They received either the ChAdOx1 nCoV-19 vaccine (n=543) or the meningitis vaccine as control (n=534).

ChAdOx1 nCoV-19 showed an acceptable safety and tolerability profile, with headache and fatigue as the most commonly reported reactions. There were no serious adverse events related to ChAdOx1 nCoV-19.

The results were “encouraging and an important milestone” in the search for a COVID-19 vaccine, said Dr Andrew Pollard, lead investigator and professor of paediatric infection and immunity,  University of Oxford.

ChAdOx1 nCoV-19 is made from a weakened version of adenovirus, a common cold virus that causes infections in chimpanzees. The virus was genetically modified to code for the SARS-CoV-2 virus spike protein.

Too early to tell

Dr Sarah Gilbert, professor of vaccinology, University of Oxford and co-author of the ChAdOx1 nCoV-19 study, said the results, while encouraging, are not to be trumpeted too soon.

“It is too early to tell … the difficulty is that we don’t know how strong that immune response needs to be,” she said. “We can’t tell, just by looking at immune responses, whether this vaccine is going to protect people or not.”

The only way to find out is to do phase III trials and “wait for people to be infected to know if the vaccine can work,” she added.

The team is now advancing to phase III trials, enrolling 30,000 patients. The speed at which the vaccine has made through the testing process is quite impressive. What usually takes years, has only taken months. If successful, Oxford’s programme would leapfrog all other COVID-19 vaccines in development.

“Yet, for any vaccine to be useful, we not only need larger studies in [places where] COVID-19 is still at a high rate. We need to be reasonably sure that the protection lasts for a considerable time,” commented Professor Stephen Evans from the London School of Hygiene and Tropical Medicine, London, UK, who is unaffiliated with the study. “The trial should also include people older than 55 years.”

mRNA vaccine candidates

Meanwhile,  preliminary results from an ongoing German phase I/II trial of an mRNA vaccine, BNT162b1, by Pfizer and BioNTech, support the positive findings from its US trial.

BNT162b1, targeting the RBD* SARS-CoV-2, produced neutralizing antibody responses in humans beyond the levels observed in convalescent sera at low doses. [medRXiv; doi:https://doi.org/10.1101/2020.06.30.20142570]

Other big players, US-based biotech company Moderna and the US National Institute of Allergy and Infectious Diseases (NIAID), are capitalizing on the newer messenger RNA technology to develop a COVID-19 vaccine.

Early data on the first 45 healthy adults (age 18–55 years) enrolled in Seattle and Emory University sites in Atlanta, US, who were vaccinated twice, at 28 days apart, with the mRNA-1273 COVID-19 vaccine (25 μg, 100 μg, or 250 μg dose), showed that the vaccine induced anti–SARS-CoV-2 immune responses. There were no trial-limiting safety concerns identified. [N Engl J Med 2020;doi:10.1056/NEJMoa2022483]

In a related commentary, Dr Penny Heaton of the Bill & Melinda Gates Medical Research Institute in Cambridge, Massachusetts, US, said  the world has born witness to the compression of the typical 3–9 years of vaccine work into 6 months. [N Engl J Med 2020;doi:10.1056/NEJMe2025111]

While the data look promising, she cautioned that much work remains to be done, partly because the 250-μg dose was linked to severe systemic side effects without increasing efficacy beyond the 100-μg dose. “It is prudent to evaluate doses of 100 μg and lower to define the regimen that provides the most appropriate benefit–risk profile for this vaccine,” she said.  A planned phase 3 trial of the mRNA SARS-CoV-2 vaccine is imminent.

Experts do not anticipate full approval of a vaccine before early 2021. But if it does arrive,  do we have enough?  Any vaccine will have to be distributed globally to stamp out the pandemic of human disaster wherein rich countries restart their economies whereas people from poor countries are left to die.

Any future COVID-19 vaccine is precious and should be universally accessible. With reports from ELAINE SOLIVEN

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