After developing and rolling out Covid-19 vaccines at record speed, drugmakers are already facing variants of the rapidly evolving coronavirus that may render them ineffective, a challenge that will require months of research and a massive financial investment, according to disease experts.

Executives from Moderna Inc and Pfizer Inc and partner BioNTech SE are considering new versions of their vaccines to respond to the most concerning variants identified so far. That is just one piece of the work needed to stay ahead of the virus, nearly a dozen experts told Reuters.

Johnson & Johnson said the concerning variant first identified in South Africa has got its attention and it will tweak its vaccine accordingly if needed. Pfizer said it could produce a new vaccine relatively quickly, but a top vaccine executive said manufacturing it presents additional challenges.

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