BioNTech SE (BNTX) shares plummeted 5.34% in pre-market trading on Monday, following news that its partner Moderna has significantly lowered its 2025 sales forecast due to weakening demand for COVID-19 vaccines.

Moderna, which collaborated with BioNTech to develop its mRNA-based COVID-19 vaccine, announced it is cutting its 2025 revenue guidance by $1 billion to $1.5 billion - $2.5 billion. This is significantly below the previous estimate of $2.5 billion - $3.5 billion and misses analyst expectations of $2.95 billion.

The lowered forecast reflects slower-than-expected uptake of Moderna's new respiratory syncytial virus (RSV) vaccine as well as waning demand for COVID-19 shots. Moderna CEO Stéphane Bancel stated the company plans to reduce cash costs by $1 billion in 2025 and an additional $500 million in 2026 to address the revenue shortfall.

While a potential secondary factor, reports also emerged that authorities in Jakarta are urging vigilance against a new virus called Human Metapneumovirus (HMPV), which could stoke concerns over future disease outbreaks and vaccine needs. However, the primary driver appears to be Moderna's downbeat vaccine sales forecast, which has raised worries over BioNTech's COVID-19 vaccine revenue stream.