Coronavirus infections are rising throughout the US again (nearly 69,000 new cases in one day) due to the highly contagious delta variant, and the virus is particularly impacting areas with low vaccination rates. More cases have started to be reported of fully vaccinated people contracting the virus. So, if you're fully vaccinated, should you be worried about getting Covid-19? Not necessarily, but don't throw away your face masks yet. 

Currently, 162 million people in the US have been fully vaccinated, nearly half of the country's total population. But across the globe only 13.3% of people have been fully vaccinated. That means more than 86% of the total global population has the potential to spread Covid-19, causing new variants like delta and lambda to emerge that can potentially infect everyone. Yet as troubling as they may appear, breakthrough infections among the fully vaccinated are quite uncommon, and the likelihood of serious illness or hospitalization is still low. 

We'll explain what a breakthrough coronavirus infection is, how it's possible for fully vaccinated people to become infected, and what it means. This information comes from the Centers for Disease Control and Prevention, the World Health Organization and other experts.

What is a breakthrough Covid-19 infection exactly?

A breakthrough Covid-19 infection happens when a fully vaccinated person becomes infected with the coronavirus, experiences symptoms, is hospitalized or dies from the infection. While rare, a small percentage of fully vaccinated people can get Covid-19 if exposed to the virus, but they're much less likely to become sick, according to the CDC. 

If someone's fully vaccinated and does test positive for coronavirus, it's likely they'll have mild symptoms (see below) or be asymptomatic, Clare Rock, a Johns Hopkins medical professor, told me on the phone. 

It isn't yet clear what role vaccinated people with Covid-19 might play in spreading infections. If you do become ill, experts urge you to isolate yourself to prevent others from getting sick -- especially people with medical vulnerabilities.

How can a fully vaccinated person become infected with coronavirus?

Someone can become infected with Covid-19 just before or right after they get the vaccination, as it takes roughly two weeks before the vaccine is most effective. However, even after the immunity builds up, there's still a chance they can become infected, according to the WHO, since the vaccines aren't silver bullets against any disease (Moderna and Pfizer are over 90% effective).

While there are still millions of unvaccinated people around the world, new variants will emerge, Rock says. For example, the delta variant currently circulating can still pose a threat to people who have received full vaccination -- especially those who have high risk medical conditions. This can potentially lead to hospitalization or even death (more below). 

Are Covid-19 symptoms still severe if you're fully vaccinated?

It's very rare for someone who's fully vaccinated to experience severe symptoms from Covid-19. People who have received both doses of the vaccine are less likely to be hospitalized or die than those who haven't been vaccinated, the CDC says. Vaccinated people typically see symptoms like a runny nose, which they mistake as a common cold, Rock said.

But that's not to say it can't happen. The CDC says some fully vaccinated people can still be hospitalized and die. This can include people who have medical conditions that make them immunocompromised, Rock said, including those with cancer and people who have had organ transplants -- in general, people who are more vulnerable.

How can you protect yourself from breakthrough infections?

If you're fully vaccinated but worried about getting sick, you can take the following precautions. 

• Wear a mask in public places.
• Social distance from those who haven't been vaccinated.
• Keep your home well-ventilated by opening windows.
• Wash your hands.
• Get a Covid-19 test if you're experiencing symptoms.

Will fully vaccinated people need to get booster shots?

At this time, there's not a clear answer. While some say a booster shot may be necessary in the future, the CDC and the Food and Drug Administration don't agree -- at least not yet. Scientists are continuing to study the immunity of fully vaccinated people to get a better idea of how well the vaccines protect them. 

However, Moderna is currently researching if and when a booster shot may be necessary. For instance, vulnerable people who don't have a robust immune system -- such as those with serious medical conditions -- may need an additional shot, Rock said.

Pfizer says it's working on a booster shot for its Covid-19 vaccine (PDF) to enhance immunity for those who have already received both doses. The UK is also prepping for booster shots, with vaccine experts in Britain saying a booster shot may be needed before winter.

Which variants are causing the breakthrough infections?

The variant causing the most concern right now is the delta variant, which is now the dominant strain in the US and other countries. This variant has caused an increase in Covid-19 cases, which is also impacting some people who are fully vaccinated. 

In comparison to the alpha variant, researchers have found delta to be 60% more transmissible, and hospitalization risks are much higher in unvaccinated people.

In most instances, the cases are happening in areas of low vaccination rates. For example, US states like Louisiana and Florida have low vaccination rates and their Covid-19 cases are surging again.

What do experts say about the efficacy of Covid-19 vaccines?

The breakthrough infections don't mean the vaccines aren't effective. "The effectiveness against severe disease is still substantial," Anthony Fauci said during a White House press briefing Thursday. "Get vaccinated. It offers good protection against disease."

The main reason for breakthrough cases is due to the number of people who still haven't been vaccinated. Once more people are fully vaccinated, it'll help reduce the spread of Covid-19 throughout the world because the virus won't be able to infect as many people.

Until then, the virus will continue to mutate and spread, creating new variants. 

CNet