New Evidence Points To Antibodies As A Reliable Indicator Of Vaccine Protection

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23 Авг 2021, 13:47

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Scientists have studied the blood of people who were part of a large trial for the Moderna vaccine to measures antibodies that can help predict levels of immunity after getting a COVID shot.

Britta Pedersen/dpa/picture alliance via Getty I

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Britta Pedersen/dpa/picture alliance via Getty I

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The results show that antibody levels can be predictive of immunity, which should help develop and test new vaccines at a much faster pace. It’s even possible COVID-19 vaccine makers may not need to conduct trials with huge numbers of people to see how many get sick after getting vaccinated. Instead, researchers could simply draw blood and look for antibody levels that correlate with protection.

«So maybe they would only need to study a couple of hundred people instead of tens of thousands if they wanted to show a vaccine was working,» Gilbert says.

No magic number yet

The four markers of immunity identified in the paper should indicate how well a COVID vaccine is working overall, but the blood test cannot tell an individual person about their level of protection.

It would be great if the antibody level was a specific number, but it’s not, says Emory University biostatistician David Benkeser, another author on the study.

«Unfortunately, the story is a bit more subtle than that,» he says. «We really view this as more of a continuum. Some antibodies [are] good. More are better.»

In fact, it’s pretty clear that antibodies alone don’t explain why some people are protected, and other parts of the immune system also play important roles in fighting off the coronavirus, including T-cells.

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«Two percent of the individuals who were vaccinated had very, very low levels, levels of antibodies that were below that lower limit of detection,» says Christopher Houchens, a biomedical researcher at the Biomedical Advanced Research and Development Authority, another author of the study. «However, about 50 percent of those individuals in that two percent of the population were still protected and did not come down with symptomatic COVID-19 disease.»

More research needed to convince federal regulators

Researchers plan to do a similar analysis of the association between antibodies and vaccine-induced immunity in people who participated in the Johnson & Johnson and AstraZeneca COVID-vaccine trials to see if the same pattern holds.

There are also plans to collect data in what are called challenge studies, where vaccinated people are deliberately infected with the coronavirus to see how well the vaccine protects them from infection or illness.

Ultimately, multiple studies will be needed to convince federal regulators that antibody levels alone can be sufficient evidence to support authorization and approval of a future COVID vaccine.

That’s not a surprise.

«Science is not simple,» says Holly Janes, a biostatistician at the Fred Hutchinson Cancer Research Center who worked on designing the antibody study. «It’s not clean and tidy. Looking at things in different ways, in different types of studies, different types of analyses and different data sources is important, and that’s how we get at the truth. There’s hardly ever one study that tells us everything we need to know.»

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