Sinovac’s chickenpox vaccine shows 87% efficacy in topline phase 3

In a temporary break from its corporate drama that includes investor class-action lawsuits, a going-private battle and long-delayed annual report, Chinese vaccine company Sinovac posted positive topline data from a phase 3 study of its chickenpox candidate.

The vaccine, designed to prevent chickenpox caused by the varicella zoster virus, was 87.1% efficacious, preliminary phase 3 data showed. The study included nearly 6,000 healthy children from 1 to 12 years old in China who were given one 0.5 ml dose of the vaccine intramuscularly prior to the chickenpox epidemic season in 2016.

Sinovac also conducted a parallel study involving 1,197 children ages 1 to 3 to evaluate the consistency of three consecutive batches of the vaccine. The company reported consistent immune response and good safety profile for all three lots, which showed that the vaccine production quality is stable.

RELATED: Sinovac to go private as bribery concerns hint at investor class-action lawsuits

According to information published on, a full readout from the phase 3 is expected at the end of this year, and Sinovac’s chairman, president and CEO, Weidong Yin, said in a statement that the company is planning for commercialization in China by the end of 2019.

Other vaccines in the space include Merck & Co.'s pediatric varicella vaccine Varivax and MMR-varicella combination vaccine ProQuad in the U.S.; while GlaxoSmithKline has Varilrix and MMRV combo vaccine Priorix-Tetra outside of the U.S. Sinovac intends to seek Chinese marketing approval with its shot.

As promising as the data are, the recent focus on the Nasdaq-listed Chinese vaccine maker has not been on its scientific portfolio, but rather on its corporate affairs as it is in a process to be taken private. In late June, it announced a $7-per-share buyout agreement with a consortium led by Yin. But that deal was soon challenged by another buyer group led by compatriot Sinobioway, which accused a special committee appointed by the board of colluding with Yin to “erode the interests of minority shareholders.”

Sinobioway made its $7-per-share offer last February when Yin’s buyer group was only offering $6.18, and later said that the committee didn’t contact them again for a counteroffer before giving the deal to Yin’s group. Sinobioway announced last month that it has submitted documents to the committee that it has sufficient funds for the transaction, while also noting that 1Globe Capital, which owns about 16.4% of Sinovac’s shares, supports its proposal in an SEC filing.

Several law firms have also piled up on a possible class action against Sinovac. Yin was found bribing a former China FDA official—who was sentenced to 10 years in prison—in exchange for smoother clinical trial and vaccine approval process. Although no charges were brought against Yin, the news tanked Sinovac’s stock and led to calls for investor class-action lawsuits.