Moderna and Pfizer shares climb after CDC calls for pause in use of J&J COVID-19 vaccine

• Shares of Moderna and Pfizer climbed on Tuesday after the CDC called for the pause in use of Johnson & Johnson's COVID-19 vaccine.
• The call from the CDC came after 6 reported rare cases of blood clots for recipients of J&J's vaccine.
• Sign up here for our daily newsletter, 10 Things Before the Opening Bell.

Investors viewed bad news for Johnson and Johnson's COVID-19 vaccine as good news for Moderna and Pfizer on Tuesday, which both climbed after the CDC called for a pause in the use of J&J's single-dose COVID-19 vaccine.

Shares of Moderna surged as much as 7%, while Pfizer and its COVID vaccine partner BioNTech jumped 1% and 3% in Tuesday trades, respectively. Shares of J&J dropped as much as 3% before paring a portion of those losses.

The CDC's guidance to pause the use of J&J's COVID vaccine came following reports of six rare blood clots in patients after receiving the single-dose. The pause comes "out of an abundance of caution," the CDC said.

So far, nearly 7 million J&J vaccine shots have been administered in the US, resulting in a blood clot rate of .00000086% if there are no more than six patients who have developed blood clots.

"CDC will convene a meeting of the Advisory Committee on Immunization Practices on Wednesday to further review these cases and assess their potential significance," the CDC said.

According to the New York Times, the pause will likely result in federal vaccination sites not using the J&J vaccine until the risk of blood clots is sorted out, and state officials will likely follow suit. Importantly, the FDA has not revoked J&J's emergency use authorization for the vaccine.

Until the risks of J&J's vaccine are sorted out, the reliance on Moderna and Pfizer's vaccine will increase as the US races to reach herd immunity from COVID-19.