Investing.com -- Novavax Inc and Moderna Inc shares declined on Wednesday after rising sharply the previous day on reports of a suspected pneumonic plague case in Russia.

Novavax (NASDAQ: NVAX) fell 11% during trading after gaining 20% on Tuesday. Moderna shares dropped 6% following a 7% increase the day before. The iShares Biotechnology ETF declined 3%, while the S&P 500 rose 1%.

The World Health Organization currently assesses the broader public health risk as low. The plague remains unconfirmed and contacts have tested negative, according to Citi.

BioNTech SE (NASDAQ: BNTX) showed limited movement, rising 1% on Tuesday before trading flat on Wednesday. Citi noted that investors increasingly value the company for its oncology pipeline rather than its COVID-19 products.

Citi stated that the price movements demonstrate the headline sensitivity affecting vaccine-focused companies. The firm expressed preference for companies developing therapies for immunology and inflammation, oncology, cardiometabolic conditions, and rare diseases.

The investment bank said vaccine companies remain exposed to volatile policy narratives and expects future headlines to continue affecting the sector.