Millions of people are getting vaccinated with COVID-19 vaccines, and most of them have already received two doses which were given 21 days apart. This is to ensure that vaccinated people are getting the most protection against the SARS-CoV-2, the virus that causes COVID-19.

Earlier this year, Science Times reported that Pfizer's CEO Albert Bourla said that they are studying to add a third dose that will hopefully enhance and provide a better shield from the variants of coronavirus and will likely raise the antibody response by ten to twenty-fold.

Adding to his previous statements, Bourla said on Thursday that it is most likely the third dose is needed within 12 months of the initial two-dose regimen for a person to get fully vaccinated, NBC News reported.

Both Pfizer and BioNTech, its German partner, are studying the duration of the vaccines' protective immunity will last to guide whether booster shots would be necessary or not.

COVID-19 Third Dose

Clinical trials on the efficacy of the Pfizer-BioNTech COVID-19 vaccine suggest that their vaccines offer high levels of protection of up to six months after the second dose without any serious side effects. Their vaccine is also effective against the variants first found in the UK and South Africa.

Moderna is also studying upgrading their vaccine to target the South African variant, which experts are concerned about because it may evade other existing vaccines.

Moderna CEO Stéphane Bancel said in an interview with CNBC that they are working on a shot that combines the protection against COVID-19 and the seasonal flu in preparation for possible variants that may emerge over the next year.

Biden administration's COVID response chief science officer, David Kessler said that it is likely Americans will receive booster shots against COVID-19 variants. He noted that although existing vaccines are highly protective, they could be challenged by new variants.

"We are studying the durability of the antibody response," he said earlier Thursday. "It seems strong but there is some waning of that and no doubt the variants challenge ... they make these vaccines work harder. So I think for planning purposes, planning purposes only, I think we should expect that we may have to boost."

Bancel told CNBC that they hope to have finished making their booster shot for its two-dose vaccine available this fall.

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Annual Revaccination Needed

Aside from a booster vaccine that should be given within the next 12 months after the second dose, Bourla told CNBC that "there will be an annual revaccination, but all of that needs to be confirmed."

He pointed out that some vaccines like the polio vaccine only need one dose but there are also vaccines like flu shots that should be taken every year. He noted that since COVID is more like influenza than a poliovirus, then it is likely that annual revaccination is needed.

His comment comes after Johnson & Johnson CEO Alex Gorsky said in February that there is a possibility that people may need vaccination every year against COVID-19, just like seasonal flu shots.

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