Officials said the limited stock of flu vaccines supplied by Chinese companies had been exhausted. Vaccines from multinational manufacturers may become available in limited quantities by late November or December.
Authorities have also warned that the shortage is creating opportunities for the sale of counterfeit vaccines.
In Lahore, drug inspectors raided a location and recovered a large quantity of suspected fake flu vaccines. Officials said two people allegedly involved in selling the suspected counterfeit products had been arrested, while proceedings to register a case were under way.
Laboratory testing and further investigations are in progress to establish the authenticity of the seized vaccines, officials added.
Drug control authorities have advised citizens to purchase flu vaccines only from licensed pharmacies. They have also urged consumers to verify batch numbers and ensure that vaccines have been stored and transported under the required cold-chain conditions.
The authorities stressed the importance of verifying vaccine authenticity amid the ongoing shortage and warned against purchasing products from unverified sellers.