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When it comes to COVID-19 variants and vaccines, many questions remain nebulous. But with new variants being discovered with frequency, how worried should we be about whether the vaccines will work against novel strains?

Dr. Peter Chin-Hong, an infectious disease specialist and professor of medicine at UCSF, breaks the variants down into three categories: the good, the bad and the ugly.

The good is the novel coronavirus strain, which started the pandemic. Chin-Hong places the strain in this category because the current vaccines do an excellent job at protecting people from contracting the virus. The Pfizer and Moderna vaccines — the only two approved vaccines for use in the U.S. — are 95 percent effective at preventing infection.

The bad includes variants such as the so-called U.K. variant, called B.1.1.7., which is thought to be up to 70 percent more transmissible than the initial coronavirus strain.

“It’s in this category because there may be some decrease in [vaccine] efficacy,” Chin-Hong said.

The ugly category features the South African variant, called B.1.351. Chin-Hong placed it in the category because it appears to highly increase transmissibility of the virus. Higher transmissibility means we may need a higher threshold for herd immunity.

Most estimates say we’ll achieve herd immunity when at least 70 percent of a region is vaccinated, but with more transmissible strains, that percentage may need to increase — to 85 percent or more.

“For the good and the bad, everyone thinks the [current] vaccines will work,” Chin-Hong said. But the picture is murkier for the South African variant. In February, for example, Pfizer said the variant could significantly reduce the number of antibodies created by the vaccine — potentially by up to two-thirds.

That’s worrisome to Chin-Hong.

“I’m worried because our vaccine rollout has been very slow around the world. It just seems like we’re playing catch up … I worry that once we vaccinate people, a variant may setup shop and eradicate our progress.”

New variants arise from replication, and replication only occurs “if noses and mouths come together,” Chin-Hong said. So the faster we can vaccinate the people, the greater the odds of stopping these variants in their tracks.

“We can’t really solve COVID until we immunize the world,” Chin-Hong said.