After reports of “white particles” found in a batch of Sanofi flu vaccine brought immunization to a halt in Hong Kong in late November, local health authorities have cleared the shots.
The questioned batch of quadrivalent seasonal flu vaccine, VaxigripTetra, passed sterility testing run by an accredited laboratory, Hong Kong’s Department of Health said Dec. 28.
Based on results from tests separately run by the agency and Sanofi, local regulators figured the batch could still be administered as long as doses had been stored properly during the one-month immunization hiatus. But a health department spokesman said the agency will continue to monitor the vaccines, and healthcare practitioners were asked to visually inspect the shots before administering them.
About 175,000 doses of Sanofi's flu vaccine supplied to Hong Kong were flagged after the particles were reported; about 75,000 of those doses had already been distributed, the local agency announced in late November. The government immediately started inspecting samples while Sanofi conducted its own investigation.
Hong Kong tested nearly 2,100 samples—about 1,300 from the affected batch and 800 from other batches—that had been stored in Sanofi’s warehouse or already dispersed to local clinics. And “no particles were detected” in those samples, the agency said. Earlier tests on different batches of VaxigripTetra also found no foreign matter.
In Sanofi’s own report, the white particles were described as inert and nontoxic cellulose, according to the agency. Sanofi concluded that the batch meets quality standards.
Sanofi’s problem in Hong Kong came soon after Taiwan’s FDA found impurities in two batches of its flu vaccines during routine inspections. Vaxigrip and another flu shot made by local firm Adimmune are given for free in Taiwan as part of a flu shot program.
Vaxigrip recently ran into hurdles in the Chinese mainland as well. Last April, the French vaccine maker said it had noticed an efficacy decline in 15 batches of the shot. Although Sanofi said the doses were still efficacious enough, it voluntarily recalled the batches as a precautionary measure. That delayed its Vaxigrip production for China this flu season and led to a sharp decline in supply.