Results from trials involving three different coronavirus vaccines released Monday, all showing positive results, with evidence the vaccines can produce immune responses that would be expected to protect people against infection.

They all also appeared to be safe, although it will take studies with more people to show how safe they really are and whether they can prevent infection.

Early results of a closely watched Phase 1/2 trial published in The Lancet suggest a coronavirus vaccine developed by the University of Oxford and AstraZeneca is safe and induces an immune response. However, researchers stressed more study is needed to know whether the vaccine protects people against the virus.

Phase 2 results for one vaccine candidate made by Chinese company CanSino Biologics were also published in the medical journal The Lancet and early results from Phase 1/2 trials of the vaccine made by Pfizer and BioNTech were released in a pre-print paper that has not yet been peer-reviewed.

The Oxford vaccine prompted an antibody response within 28 days and a T-cell response within 14 days, according to the results published Monday. Neutralizing antibodies -- so-called because they can neutralize the virus -- were detected in most participants after one shot, and in all of them after two.

That’s good news, researchers said. “The immune system has two ways of finding and attack- ing pathogens -- antibody and T cell responses. This vaccine is intended to induce both, so it can attack the virus when it’s circulating in the body, as well as attacking infected cells,” University of Oxford pediatrician Dr. Andrew Pollard, the study’s lead author, said in a statement.

A Phase 1 study typically studies a small number of people and focuses on whether a vaccine is safe and elicits an immune response. In Phase 2, the clinical study is expanded and the vaccine is given to people who have characteristics -- such as age and physical health -- similar to those for whom the new vaccine is intended, according to the US Centers for Disease Control and Prevention. In Phase 3, the vaccine is given to thousands of people and tested for efficacy and again for safety.

Phase 2/3 trials of the Oxford/AstraZeneca vaccine are currently underway in the UK, Brazil and South Africa, and later-phase trials are expected to start in the United States in August.

There were no serious adverse event related to the vaccine; fatigue and headache were the most commonly reported reactions. Other common side effects included pain at the injection site, muscle ache, malaise, chills, feeling feverish and high temperature.

‘There’s A Long Way To Go’

These Phase 1/2 results were promising, researchers said, but large-scale trials are needed to determine whether the vaccine protects against the coronavirus.

“The key elements required to proceed to a Phase 3 trial are all there,” Stephen Evans, a profes- sor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine, told the Science Media Center in the UK about the Oxford trial.

“The responses measured in the blood and the absence of serious harms indicate there is a possibility of an effective vaccine against Covid-19. It does not yet show that the disease is reduced or prevented, and this will not be easy to show until phase 3 trials have been completed in settings where the SARS Cov-2 virus is circulating at a high rate and people are getting clinical and severe disease.”

Oxford vaccine expert Adrian Hill said the team is looking at trying both one and two doses in Phase 3 participants.

AstraZeneca says it has secured capac- ity to produce 2 billion doses of the vaccine. “If possible, there’ll be a vaccine being used by the end of the year,” Hill said.

There are 23 Covid-19 vaccines currently in clinical trials globally, according to the World Health Organization.

CanSino Vaccine Phase 2 Results Published

More Phase 2 results published Monday suggested CanSino Biologics’ vaccine was safe and created an immune response. The trial, conducted in Wuhan, China, in April, involved more than 500 people given high, low or placebo doses of the vaccine, the release said.

The trial found that 95% of the participants in the high dosage group and 91% in the low dosage group showed either T-cell or antibody immune responses 28 days after vaccination. In the high dosage group, neutralizing antibody responses were induced in 59% and binding antibody responses in 96%. Bind- ing antibodies attach to a virus but don’t stop it from infecting cells.

About half of people who got the low dose developed neutralizing antibodies.

Most adverse reactions were mild or moderate. Nine percent of the participants in the high-dose group had severe adverse reactions within 28 days, the most common of which was fever.

In a commentary also published in The Lancet, Naor BarZeev and Dr. William J. Moss of the International Vaccine Access Center and Johns Hopkins Bloomberg School of Public Health wrote that the trials were “broadly similar and promising,” and the safety data “reassuring.”

But questions remain about how long an immune response will last and how the vaccines will impact older populations, people with particular health conditions that put them at risk, and racial and ethnic groups more severely affected by Covid-19, they said.

“When things are urgent, we must proceed cautiously,” they wrote. “The success of COVID-19 vaccines hinges on community trust in vaccine sciences, which requires comprehensive and transparent evaluation of risk and honest communication of potential harms.”

More Vaccine Data From Pfizer, BioNTech

Also, on Monday, US pharmaceutical com- pany Pfizer and German biotechnology company BioNTech reported their Covid-19 vaccine candidate elicited a “robust” antibody and T-cell immune re- sponses in an early Phase 1/2 study.

The data has not yet been published in a peer-reviewed medical journal, but was published in a pre-print paper to the online server medRxiv.org on Monday.

The findings mirror previous data among US participants in the study, which were announced earlier this month.

The German trial included 60 healthy adults ages 18 to 55 who were randomly assigned to receive varying doses of the vaccine.

The release also notes that there were some local reactions and mild to moderate adverse events, including some with flu-like symptoms and injection site reactions. All events resolved spontaneously and were managed with simple measures, according to the release. No serious adverse events were reported.

A Phase 3 vaccine trial that might involve up to 30,000 healthy participants is expected to begin in late July, if it receives regulatory approval, BioNTech and Pfizer said.

www.ox.ac.uk www.astrazeneca.com