Shares of drugmakers involved in the production of COVID-19 vaccines, including Pfizer (PFE.N) and Moderna (MRNA.O), fell on Thursday, a day after U.S. President Joe Biden’s plan to back intellectual property waivers on vaccines.

Biden threw his support behind a World Trade Organization waiver of intellectual property rights on vaccines to increase their availability to poorer nations including India, which is under the grip of a massive second wave of infection.

Implementing such a move could be a lengthy process, with all 164 WTO member countries required to arrive at a consent, but it could dent revenue and profit for companies that have invested heavily in the vaccines.

"It could clearly reduce potential revenues some of these firms were expecting to generate from licensing their patents", said Neil Wilson, chief market analyst at Markets.com.

Shares of Pfizer, Moderna, Novavax (NVAX.O) and U.S. shares of BioNTech were all down between 2% and 6% before the bell. BioNTech's Frankfurt-listed shares fell as much as 19% and were down 13% by 1029 GMT.

Pharma shares lost ground elsewhere too, with Germany's Curevac (5CV.DE), which has sought approval for its COVID-19 vaccine, tumbling as much as 15%.

Shares in Chinese vaccine makers slumped with CanSino Biologics Inc , a single-dose COVID-19 vaccine maker, down 16%. Its Hong Kong shares (6185.HK) dived as much as 22%.

However, shares in London-listed AstraZeneca (AZN.L) were unchanged however. Europe's index of healthcare stocks (.SXDP) was down 0.5%, slightly lagging the pan-European STOXX 600 benchmark.

Jefferies analyst Michael Yee said any suggestion that other countries could just manufacture and override patents will likely decrease investor confidence in the business models during a pandemic.

Yee, however, cautioned that manufacturing supplies, raw materials, vials, stoppers, and other key materials are in limited supply for 2021 to matter for the ongoing situation in India and South Africa.