Authorities are trying to contact thousands of patients vaccinated by two Sydney GPs after vaccines were found to have expired or not been stored properly.

Thousands of patients of a Sydney GP clinic - including children - may need to be re-vaccinated after it was discovered some shots were incorrectly stored or had expired.

NSW Health on Wednesday warned vaccines administered by doctors Darrel and Brinda Weinman at their Burwood practice since 2010 may not have been effective.

It includes shots for measles, mumps and rubella, meningococcal, pneumococcal and other adult vaccines.

Sydney Local Health District's Dr Leena Gupta said patients are being advised to see a new GP about the need for revaccination.

"The actual ineffective vaccines won't do them any harm but they do need to be revaccinated," she told AAP.

Authorities aren't concerned about those who were immunised against the flu, mainly because it is given every year, or travel vaccines - which weren't stored at the practice.

About 3000 patients have already been contacted but inconsistent record-keeping at the practice has made it difficult for authorities to identify patients and obtain contact details.

NSW Health was notified of the issue at the end of March following a complaint and immediately started an investigation.

Authorities found the GPs did not adhere to the strict national guidelines for storing vaccines, which includes rules around temperature monitoring, fridge types, and annual auditing.

"In this case, none of that was adhered to," Dr Gupta said.

The long-standing practice operated out of a house on Lindsay Street. Dr Brinda Weinman retired in May, while Dr Darrel Weinman died in October.

NSW Health said it is helping the Medical Council of NSW and NSW Health Care Complaints Commission to investigate and respond to the incidents.