AstraZeneca (NYSE:AZN) continues to get back on its feet after clinical trials for its coronavirus vaccine candidate were halted. On Tuesday, South Africa's Department of Health said the company had resumed the part of the trials taking place in that country.

The news came over a week after the U.K. trial of AZD1222 was halted due to one participant developing a side effect (which was not specified). It also came three days after that study was given the green light to restart. That was granted after an independent committee overseeing the British trial informed that country's Medicines Health Regulatory Authority that it felt it was safe to relaunch the study.

A syringe being filled with a vaccine from a vial.

Image source: Getty Images.

In addition to the U.K. and South Africa trials, AstraZeneca is also conducting studies in Brazil and the U.S. 

Among the many competitors in the race to develop a vaccine for COVID-19, AstraZeneca is a front runner. AZD1222 is one of the few candidates that has advanced to late-stage testing (it is currently in phase 2/3 trials). Although delays are not unusual in late-stage pharmaceutical testing, the particularly high-stakes nature of the coronavirus vaccine "race" leaves little margin for error in the eyes of some investors.

While AZD1222 has as good a chance as any as the first vaccine candidate to win major regulatory approval, investors should bear in mind that no candidate is a lock for clinical trial success, let alone such permission.

Nevertheless, this latest piece of news about AstraZeneca helped boost the stock 2.3% higher on Tuesday, exceeding the rise of the S&P 500 index.