The denial came in response to two articles published in the German papers Handelsblatt and Bild, which both suggested the Oxford/AstraZeneca jab has an efficacy of less than 10 per cent for the elderly.
German officials now fear the vaccine might not be approved by the European medical regulator for those over 65, according to Bild.
AstraZeneca strongly denied the claims in a written statement, saying that “reports that the AstraZeneca/Oxford vaccine efficacy is as low as 8 per cent in adults over 65 years are completely incorrect”.
The company added that its jab was approved without an upper age limit by Britain’s Joint Committee on Vaccination and Immunisation in December.
The organisation also cited test data published in the Lancet in November, showing that all older adults generated antibodies following their second vaccine dose.
However, researchers at Oxford University wrote in the same health journal on 8 December that the efficacy data for older adults was limited.
“Efficacy data in these cohorts are currently limited by the small number of (infection) cases, but additional data will be available in future analyses,” they wrote.
The data is less comprehensive for older groups because the main AstraZeneca trial in Britain started by only testing those aged under 55.
As well as facing questions about the efficacy of its vaccine, AstraZeneca has recently become embroiled in a row with the EU, after it told the bloc on Friday that its first vaccine deliveries would be up to 60 per cent lower than initially promised.
The ensuing fallout led the EU’s health commissioner Stella Kyriakides to say that all companies manufacturing Covid-19 vaccines in the EU “will have to provide early notification whenever they want to export vaccines to third countries”.
The threat to block the export of vaccines could have implications for the UK’s vaccine supply, as the Pfizer vaccine is made in Belgium.
Speaking on Tuesday, Nadhim Zahawi, the minister for Covid vaccine deployment, said he was confident the UK’s mass immunisation programme would not be adversely affected.
“I’m confident that they (AstraZeneca and Pfizer) will both deliver for us the quantities that we need to meet our mid-February target and of course beyond that,” he told Sky News.
The UK plans to give roughly 15 million people their first dose of the vaccine by mid-February.
Additional reporting by agencies