The city reached an agreement with AstraZeneca for 7.5 million doses of its Covid-19 vaccine, Chief Executive Carrie Lam said at a media briefing Wednesday. The deal joins similar agreements with Pfizer Inc.-BioNTech SE and Chinese developer Sinovac Biotech Ltd., giving the city a total of 22.5 million potential doses of vaccines. Hong Kong is seeking a further 7.5 million doses and residents will be offered a choice of which vaccine they will take, according to Lam.

While the move will address concerns from residents anxious about taking a Chinese vaccine, it also raises the prospect of a run on particular shots. The three candidates are widely different and none of them have been approved for use in the city yet, which is enduring its fourth wave of the pandemic. In a bid to encourage take-up of the vaccines, Lam said on Wednesday the government will set up a fund to provide financial support for patients that experience side effects.

Pfizer’s vaccine, which data indicate has a 95% protection rate against Covid-19, uses a new technology called messenger RNA that turns the body’s own cells into vaccine-producing factories to fight the coronavirus. While the shot is considered to be safe, there have been some reports of serious allergic reactions.

Sinovac’s shot is made using an inactivated version of the coronavirus that is said to prime human immune systems to fight it. The vaccine was found to be more than 50% effective in a Brazilian clinical trial, though researchers delayed releasing more information at the request of the company. AstraZeneca’s vaccine has the most supply deals around the world, but initial clinical results were mixed.

Lam said Wednesday the government has appointed a committee to approve the emergency use of the vaccines, signaling the city is moving closer to authorizing the candidates.

Countries lacking the capacity to independently validate experimental drug therapies often rely on reviews of global leading drug authorities like the U.S. Food and Drug Administration. Pfizer-BioNTech’s shot has so far been approved in the U.S. and the European Union, while Singapore approved it last week.

Bloomberg reported earlier this month that Shanghai Fosun Pharmaceutical Group Co., the Chinese company with the rights to market the Pfizer-BioNTech vaccine in Hong Kong, was preparing to seek approval of the shot soon after the U.S. cleared it.