As millions of Americans get vaccinated against COVID-19 each day, scientists are on a vigorous hunt to tackle several moving targets — at least five coronavirus variants of concern in the U.S. — that may be able to evade the shots’ defenses.

Early evidence shows some of the variants can sidestep protection from the currently available COVID-19 vaccines from Pfizer, Moderna and Johnson & Johnson by reducing the effectiveness of the antibodies gained from vaccination. That’s because the variants contain mutations, or changes, in the coronavirus’s spike protein.

That spike protein, which enables the virus to enter human cells, is also used by the vaccines to prime our immune systems to recognize and fight the coronavirus.

However, experts say the vaccines generate a broad immune response that includes a range of antibodies and cells, so “changes or mutations in the virus should not make vaccines completely ineffective,” according to the World Health Organization.

Preliminary data reveals that current vaccines are still able to prevent coronavirus-related hospitalizations and deaths, even though overall protection against symptomatic COVID-19 is lowered.

Experts worry this suggests immunity gained from currently available vaccines may dwindle earlier than expected.

“For right now, you know that a line is crossed if you see people fully immunized with the vaccines [who], nonetheless, when infected with the variants, are being hospitalized,” said Dr. Paul Offit, director of the Children’s Hospital of Philadelphia’s Vaccine Education Center, the journal JAMA reported.

Data on COVID-19 vaccines and variants

Although all three COVID-19 vaccines offer protection against severe disease and death, it’s difficult to compare them and their ability to work against variants.

The Johnson & Johnson vaccine is so far the only shot authorized for emergency use in the U.S. that has been tested against the variants in a lab setting. Clinical trials showed it was 72% effective at preventing moderate to severe COVID-19 among Americans.

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That can explain why its efficacy rate was lower than that of Pfizer’s and Moderna’s, both of which were tested before the variants emerged from the U.K., Brazil and South Africa (two new variants from California have since surfaced; it’s unclear how these versions interact with any of the vaccines).

Yet, the most alarming data continues to stem from the variant that emerged from South Africa. When tested against it, the Johnson & Johnson shot’s efficacy dropped to 64%.

Moderna said there was a “sixfold reduction” in its vaccine’s antibodies’ effectiveness against the variant from South Africa, but levels of the protective proteins remain above those “that are expected to be protective,” McClatchy News previously reported. Meanwhile, Pfizer’s vaccine appeared to produce sufficient antibodies against it.

On the other hand, there’s minimal impact on antibody effectiveness from either of the vaccines when put up against the variants that emerged from the U.K. and Brazil.

Still, efficacy rates determined during clinical trials are those of controlled settings. Scientists are still learning how effective the vaccines are in real life, but emerging evidence shows the vaccines are preventing asymptomatic and symptomatic infections relatively well in the general population.

What vaccine developers are doing to tackle coronavirus variants

As more data is collected in real-world settings, scientists are preparing for the worst.

“It is unclear whether changes in vaccine composition will be needed to effectively control the COVID-19 pandemic; however, it is prudent to be prepared,” wrote Dr. Anthony Fauci, medical adviser to President Joe Biden and director of the National Institute of Allergy and Infectious Diseases (NIAID), together with two other NIAID colleagues in JAMA.

Pfizer announced in February that it will test whether a third dose of its vaccine — what the company calls a booster shot — will increase immunity against the currently circulating coronavirus variants and any future ones that might emerge. The company will recruit participants who were a part of its early stage study in the U.S. to receive the booster.

It is also planning on testing a new “variant-specific vaccine” designed to tackle the variant first identified in South Africa.

Moderna has similar plans. In January, the company said it was developing a booster “with strain-specific spike proteins” against the variants from South Africa that could be administered after two doses of the original shot, “out of an abundance of caution.” A month later, Moderna announced it shipped the booster shot to the NIAID to begin an early-stage study in people.

Johnson & Johnson also said it will launch an early stage study to test a restructured vaccine that would protect against variants this summer.

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