Dr. Scott Gottlieb on Thursday warned coronavirus vaccine recipients not to abandon their guards immediately, telling CNBC that it was still important to comply with public health measures such as wearing a face mask.
The former commissioner for the U.S. Food and Drug Administration said the advice is especially important to older Americans who are at higher risk of death or serious illness from Covid-19.
"I think for an elderly person who is susceptible to this virus, wait some time after the second shot until you probably have full protective immunity," Gottlieb told Squawk Box. "I don't think people should feel completely safe after the first shot."
Both Covid vaccines, which have received emergency clearance from the FDA, require two doses. Pfizer and its German partner BioNTech developed one of the vaccines while Moderna makes the other. Gottlieb is on the Pfizer board of directors.
Around 10.3 million Americans received their first Covid shot on Wednesday morning, according to the Centers for Disease Control and Prevention. About 29.4 million cans were distributed.
The shaky vaccine comes as the nation continues to see high levels of coronavirus infections and more deaths from Covid-19. According to a CNBC analysis of the data compiled by Johns Hopkins University, the 7-day average of new daily cases in the country is 245,306. Over the past week, an average of 3,360 Americans have died of Covid-19 each day. This is the second highest number ever recorded.
Vaccine recipients still need to take public health precautions as the US outbreak remains so significant and "infections are everywhere," Gottlieb said. "If you are a vulnerable person, it is still very advisable to continue wearing a mask and taking precautions even after you had the second shot and believe you have complete protective immunity to the vaccine."
"That doesn't mean you have to hibernate and avoid seeing family," added Gottlieb, who headed the FDA in the Trump administration from 2017 to 2019. "Maybe you can lean forward in that regard but wear a mask. Be more careful with these interactions, because in a high-circulation environment you are still at risk."
As more Americans get vaccinated against Covid-19, Gottlieb said it should lower overall infection rates in the United States and significantly reduce the intensity of the epidemic. At this point he said it made more sense to "loosen" some precautions.
"Hopefully this will be summer, spring, when these new variants fail to gain a foothold here in the US and change our trajectory," he said, referring to the coronavirus strains originally found in the UK and South Africa believed to be more transmissible.
Researchers in Ohio said Wednesday they had discovered two new variants that likely originated in the United States.
Last week, Gottlieb warned Americans that a return to pre-pandemic life was unlikely in 2021. For example, he told CNBC that public places may still require that the temperature be taken before entry.
"I just think that if you drive through an airport now after 9/11, things will be different just like they are," he said last week. "I don't think masks will be mandatory next fall and winter when we can increase the vaccination rate and when these new varieties go away or don't prevail. But I think a lot of people will want to wear masks and that's fine. "
Disclosure: Scott Gottlieb is a CNBC employee and a member of the boards of directors of Pfizer, the genetic testing startup Tempus, and the biotech company Illumina. He is also co-chair of the Healthy Sail Panel of Norwegian Cruise Line Holdings and Royal Caribbean.