Will Moderna COVID vaccine need a third dose? Here’s what we know so far

Katie Camero
·3 min read

Vaccine developers are racing to test and determine if their shots will eventually require an extra dose or booster shot to maintain protection against COVID-19, but it still remains unclear how long immunity from coronavirus vaccines and natural infection lasts.

The latest information on booster shots comes from Moderna CEO Stéphane Bancel, who this week said the company will make a third booster vaccine available to Americans by the fall, CBS News reported. The vaccine currently requires two doses for maximum protection.

The goal of a third dose is to further boost immunity for COVID-19 as more contagious coronavirus variants continue to spread in the U.S., some of which have been shown to evade the shots’ defenses. Federal health officials have not officially recommended booster vaccines, citing a lack of scientific data.

Results from a preclinical study showed that a modified version of the original Moderna vaccine designed to tackle the variant that emerged in South Africa was capable of increasing antibody levels in those who already received two doses. Previous data revealed the variant lowered antibody levels by sixfold in laboratory tests.

The booster news comes a week after Pfizer CEO Albert Bourla said during a CVS Health livestream that it seems “likely” people who received the Pfizer vaccine — the first to be authorized for emergency use in the U.S. — will need a third dose “somewhere between six and 12 months, and then from there, there would be an annual revaccination.”

“But all of that needs to be confirmed, and again, the variants will play a key role,” Bourla added.

Pfizer’s chief medical officer told CNBC on Wednesday that she agrees with Bourla.

“We see indications for this also in the induced, but also the natural immune response against SARS-COV-2 [the virus that causes COVID-19],” Dr. Ozlem Tureci told the outlet. “We see this waning of immune responses also in people who were just infected, and therefore [it’s] expected with the vaccines.”

Dr. Anthony Fauci, President Joe Biden’s chief medical adviser, said we’ll likely know by this fall whether booster COVID-19 vaccines will be necessary.

“When the slope starts coming down you can predict when you’re going to get below the safe level or you could start seeing breakthrough infections,” Fauci said Sunday on ABC’s ‘This Week’. “I believe by the time we get to the end of the summer and the beginning of the fall, we’ll have a pretty good idea of whether we definitely or not need to give people boosts and when we need to give it to them.”

The reality for COVID-19 vaccines will likely mirror that of flu shots, which require annual vaccinations that are updated by scientists each year depending on which strain of the influenza virus is circulating.

Johnson & Johnson CEO Alex Gorsky also told CNBC in February that coronavirus vaccines may need to be an annual event.

Both Pfizer and Moderna announced that their vaccines offer protection against COVID-19 for at least six months. That’s just as long as researchers have been studying the vaccine’s effectiveness in a late-stage trial, meaning the vaccine’s protection may last longer than that.

Clinical trials have shown both two-dose vaccines had efficacy rates of about 95% against symptomatic COVID-19 in lab settings. That means those who get vaccinated with the Pfizer or Moderna shots benefit from about a 95% lower risk of developing COVID-19 compared to those who are not vaccinated.

More than 89.2 million Americans have been fully vaccinated as of April 22 — about 27% of the total population — according to a Centers for Disease Control and Prevention tracker.

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