The experimental CoronaVac chemically inactivated whole vaccine from Sinovac Biotech Ltd. can provide sufficient protection against COVID-19 while amenable to storage in ordinary household refrigerators.

A study published in the peer-reviewed medical journal The Lancet Infectious Diseases found CoronaVac triggered a quick immune response to COVID-109 infections. The level of antibodies produced by CoronaVac, however, was lower in people that had recovered from the disease, preliminary trial results based on preliminary trial results revealed Wednesday.

Researchers warned the vaccine's early to midstage trials weren't designed to assess its efficacy. The preliminary findings confirm CoronaVac can provide sufficient protection based on their experience with other vaccines and data from preclinical studies with macaques.

The findings were based on results in phase one and phase two clinical trials in China involving more than 700 participants.

"Our findings show that CoronaVac is capable of inducing a quick antibody response within four weeks of immunization by giving two doses of the vaccine at a 14-day interval," said Dr. Zhu Fengcai, one of the authors of the paper.

"We believe that this makes the vaccine suitable for emergency use during the pandemic

An advantage enjoyed by CoronaVac over other vaccines such as those from Pfizer/BioNTech and Moderna is its tolerance for temperatures not in the subzero range.

CoronaVac can be a more attractive option compared to the synthetic messenger RNA vaccines from Moderna and Pfizer/BioNTech because it can be stored at normal refrigerator temperatures of 2 to 8 degrees Celsius (36 F to 46 F). CoronaVac can also remain stable for up to three years, said Gang Zeng, a Sinovac researcher involved in the study.

The study said CoronaVac "offers some advantages for distribution to regions where access to refrigeration is challenging."

In contrast, vaccines developed by Pfizer/BioNTech and Moderna require far, far colder storage. Pfizer's vaccine must be stored and transported at -70 C but can be stored for up to 15 days in a thermal shipping box. This vaccine can be stored in a normal fridge for up to five days.

Moderna's candidate vaccine needs to be kept at -20 C for storage of up to six months. It will likely remain stable at normal fridge temperatures for 30 days.

CoronaVac is one of three experimental COVID-19 vaccines now being used in China to inoculate hundreds of thousands of people under an emergency use program. It is being considered by Brazil and Indonesia for inoculations by early 2021.

Sinovac is also conducting three phase three trials in Indonesia, Brazil and Turkey.