The clinic staff registered the vaccines with the wrong and expired batch numbers on the inoculation certificates issued to recipients, leading to a mismatch.

Vaccines involved in recent online reports about suspected inoculations of expired vaccines into children in Shangluo City in northwest China's Shaanxi Province have proved to be valid, said the National Health Commission on Thursday.

The online reports mainly involve five kinds of vaccines including those against DPT, ECM, and MMR, which were inoculated by three vaccination clinics in the city, according to the commission.

On-site inspections showed all the vaccines were inoculated within the term of validity, the commission said in a statement on its website.

The clinic staff, however, registered the vaccines with the wrong and expired batch numbers on the inoculation certificates issued to recipients, leading to a mismatch, according to the statement.

The wrong batch numbers were copied from an outdated list and not verified during the inoculations, which violated the standard inoculation procedure, said the statement.

The three vaccination clinics were also found to be understaffed, equipped with substandard facilities, and under lax supervision.

The investigation team has asked the local government to work out plans for rectification, conduct inspection and supervision on vaccination institutions, and fix loopholes in vaccine management.