Recent reports of breakthrough cases of COVID-19 in vaccinated individuals sparked worry among many Americans, who feared that the coronavirus vaccines are not effective after all.

But health experts continue to stress that these cases are no cause for concern when considering how vaccinated Americans have generally fared.

“The CDC offers guidance, and that guidance is taken very seriously,” Dr. Howard Forman, Yale School of Public Health professor, said on Yahoo Finance Live (video above). “It’s important to convey to the public the confidence they have and what we know right now. What we know right now is that vaccinated people are exceedingly safe, that the breakthrough cases are very, very low.”

There are currently 154.5 million Americans (roughly 59.8%) who have received at least one dose of the COVID-19 vaccine and 122.2 million who are fully vaccinated. In comparison, there have only been 1,359 reported breakthrough cases that led to hospitalizations or deaths, as of May 10, according to CDC data.

This is part of the reason why the CDC recently issued new guidance stating that fully vaccinated individuals do not need to wear face masks in outdoor and most indoor settings.

“To my knowledge, we still don’t have an identified case of a vaccinated person spreading to another vaccinated person,” Forman said. “When you add those things up, it really says that we need to have a different set of rules and guidelines for vaccinated individuals.”

That lack of vaccinated-to-vaccinated transmission is crucial as more and more vaccinated individuals interact in closer settings.

“If I’m in rooms with people who I know to be vaccinated, particularly at my work if my employer requires to be vaccinated … that changes the environment for me because it means that everybody in my workplace is verified to be vaccinated,” Forman said. “That is a game changer for my workplace. That can be a game changer for other people’s workplaces.”

Breakthrough cases

The outbreak of COVID-19 within the New York Yankees baseball team is among the most notable recent breakthrough cases. Over the past week, nine members (including players, staff, and other personnel) have tested positive for COVID-19, despite all being fully vaccinated.

Yet only one of those positive cases presented actual symptoms, with the others being asymptomatic.

Brian Cashman, general manager for the Yankees, stated that this demonstrated the efficacy of the vaccines — that while vaccination didn’t guarantee 100% protection from contracting the virus, it drastically minimized the severity of symptoms from the disease.

“When you read the fine print, they tell you that you still could get the COVID, and the vaccine is to protect you from the symptoms,” Cashman said. “It’s not full protection… The one thing I take from this is I believe the vaccine is working. We’ve got eight positives, and seven of the eight presented as without symptoms, so without testing, you wouldn’t have even known.”

All eight players who tested positive had received the Johnson & Johnson (JNJ) vaccine, which is said to be 66.3% effective at preventing the virus, in comparison to the Moderna (MRNA) and Pfizer (PFE) vaccines which have efficacy rates of 94.1% and 95% respectively. However, the J&J vaccine was a popular choice among MLB players because it only requires one dose, meaning they wouldn’t have to miss much playing time from any side effects.

In another breakthrough case, television personality Bill Maher also tested positive for COVID-19 after being fully vaccinated. He tweeted to his followers that he felt “perfectly fine.”

'We may be in the eighth or ninth inning'

Though the CDC’s latest recommendation indicates that vaccinated individuals are safe without masks, Forman said that doesn’t mean the mandates are going away in some places.

“It does not mean that we’re getting rid of mask mandates, quite frankly, because if you’re not vaccinated, you should still be socially distancing,” he said. “You should still be wearing a mask. In many settings, you probably should continue getting tested on a regular basis to protect those around you.”

Mask mandates are still in effect on public transit across the country, and likely will remain so until Sept. 14, when the order expires.

“I will not have a conversation with somebody that I meet on the street without a mask on, without socially distancing, facing that individual right now … Unless I know somebody is vaccinated, I’m still going to protect myself, even though I know, as somebody who’s been vaccinated for four months at this point, that the likelihood of me getting symptomatic disease is very, very low. I’m still going to do what I can to minimize even that small risk to begin with,” Forman said.

Despite more and more restrictions being lifted, Forman said that now is not the time for anyone to let their guard down just yet.

“In my opinion, even though others have said the sixth inning, I think we may be in the eighth or ninth inning,” Forman said. “But we cannot give up the game right now because there’s still time to lose it if we’re not careful.”

Adriana Belmonte is a reporter and editor covering politics and health care policy for Yahoo Finance. You can follow her on Twitter @adrianambells and reach her at adriana@yahoofinance.com.

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