Stocks of COVID-19 vaccine developers skidded on Wednesday after the US Centers for Disease Control and Prevention (CDC) indicated that the highly transmissible Delta variant makes up close to 52% of cases in the country, reported Investor's Business Daily.

Moderna stock toppled 4.9% and BioNTech's slipped 3.6%, while Novavax, which does not yet have an authorized vaccine, slumped 13.7%, the news source said.

Meanwhile, the Beta variant, which was first identified in South Africa, accounts for a small fraction of US cases, at 0.2%, but the Gamma variant, first found in Brazil, is responsible for 8.9% of cases in the US, the CDC estimates.

The Delta strain is gaining significant speed in the US, where just two weeks ago, it accounted for slightly above 30% of cases there, trailing the Alpha variant at 44.2%. In mid-April, the oldest data available show the Delta mutation was responsible for a tiny fraction of US cases.

The news source says vaccine stocks are pivoting to tackle the Delta mutation. Moderna pitted its vaccine against a handful of variants. Serum from eight vaccinated people generated neutralizing antibodies in response to Beta, Kappa, Delta, Eta and mutations first found in Uganda and Angola.

Johnson & Johnson, which has a one-dose vaccine authorized in the US, said its inoculation showed "strong, persistent activity against the rapidly spreading variant and other highly prevalent SARS-CoV-2 viral variants."