COVID-19: Infection Spikes, Vaccine Rates, and Variants, Explained

Published on: Sep 7, 2021fb-roundtwitter-roundemail-round
A healthcare worker fills a syringe with Pfizer Covid-19 vaccine at a community vaccination event in California.Getty Images

About half of the US population is now fully vaxxed. But COVID-19 is still a problem. While US vaccination rates increased because of the delta variant, it also ushered in a new wave of COVID-19 infections.

Why’s that?

Let’s back up: variants happen when a virus’s genes change or mutate. The word ‘mutate’ might sound scary, but it’s actually normal. As the virus spreads, it makes copies of itself. And sometimes, not all of the same instructions make it into the new copy. So it becomes a different version (aka a new strain or variant). Typically mutations aren’t a big deal because they don’t always change how a virus behaves.

Enter: the delta variant (aka B1617). First detected in October in India, this variant contributed to the devastating surge of infections there earlier this year. The World Health Organization has called it “the most transmissible of the variants identified so far.” And it’s been found in at least 132 countries. The CDC has labeled it a “variant of concern” and as of early July it’s been the dominant strain in the US.

Scientists have also discovered a variant dubbed “delta plus.” It was first detected earlier this year, and some experts say it may be even more transmissible than the delta variant. It’s been discovered in a number of countries, including South Korea, India, the US, and the UK. But as of early August, the CDC hasn’t labeled it a “variant of concern,” and some experts suggest that it’s not a major threat at this point.

Another variant that experts are keeping on watch is mu (aka B1621). It was first detected in January in Colombia. The World Health Organization has labeled it a “variant of interest” – which is considered less serious than a “variant of concern” (more on those below). Mu has been found in 39 countries, including the US. The org said that the variant could swipe left on immunity provided by antibodies. (Meaning: It may be able to cause infection in a person that is fully vaxxed or already had COVID-19.) But more research needs to be done before any conclusions can be made. In early September, Dr. Anthony Fauci said that while the US is watching the variant, it’s not “an immediate threat right now.”

The good news? Experts say that the vaccines available in the US are believed to be highly effective against the newer variants. Important, because 99% of people who died from COVID-19 in June were unvaccinated. After President Biden missed his July 4 goal of getting 70% of American adults at least partially vaccinated (a milestone that was reached in early August), he announced measures to get more people inoculated, including door-to-door outreach programs, making vaccines available at workplaces, encouraging employers to offer PTO for employees to get a shot, and stepping up efforts to get vaccines to pediatricians to provide shots to those 12-18 years old.

What other variants do I need to know about?

The CDC considers a few variants to be “of concern.” That does not include the mu variant (see: above), but it does include delta as well as…

  • Alpha. Aka B117. It was first detected in September in the UK. It’s spread to at least 182 countries, and was previously the dominant strain in the US in the spring. The CDC says it’s believed to be about 50% more contagious and could potentially cause more severe illness. Experts say that the vaccines currently available seem to offer good protection against the alpha variant.

  • Beta. Aka B1351. It first emerged in October in South Africa, and has spread to at least 131 countries. It’s been found to be about 50% more transmissible, and there are concerns that vaccines may not be as effective when it comes to this variant. Researchers have found that the variant includes mutations that may make it easier for it to evade antibodies.

  • Gamma. Aka P1. This variant was detected in January after four travelers went from Brazil to Japan. The WHO says it’s been found in at least 81 countries. It helped fuel a surge of cases in Brazil in late 2020, and quickly spread to other areas of South America. Similar to the beta variant, gamma has mutations that the Mayo Clinic says may help it evade antibodies generated by a COVID-19 infection or vaccine.


The US is in a critical period of combating the coronavirus as it deals with a spike in cases and dangerous variants. As scientists continue to detect new variants and learn more about existing ones, it’s still as important as ever to keep practicing the basics if you’re not vaccinated. And for those that are, it’s important to keep up with the latest guidelines here.

Last updated on September 7 – Updated to include details on the mu variant.

Last updated on August 10 – Updated to include latest information on variants, including the highly contagious delta variant.

Skimm'd by Maria Martinolich and Kamini Ramdeen

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