Massive amounts of H5N1 vaccine would be needed if there’s a bird flu pandemic. Can we make enough?

But the first signs that H5N1 — or any new flu virus — was starting to spread from person to person would trigger a race to produce massive amounts of vaccine to try to mitigate the damage a flu pandemic might be expected to cause. While the 2009 H1N1 pandemic is estimated to have killed about a quarter-million people worldwide — severe flu seasons sometimes kill more — the 1918 Spanish flu pandemic is believed to have killed between 50 million and 100 million people, many times more than Covid-19.