VACCINE volunteers still needed, scientists say.

Experts: Drugs still in works

Two covid-19 vaccines might be nearing the finish line, but scientists caution it’s critical that enough people volunteer to help finish studying other candidates in the U.S. and around the world.

Moderna Inc. and competitor Pfizer Inc. recently announced preliminary results showing their vaccines appear more than 90% effective, at least for short-term protection against covid-19.

If those early results hold up and U.S. regulators agree that the shots are safe, emergency use of small, rationed supplies could start in late December. Other countries with contracts for early doses would undertake their own reviews.

But multiple vaccines will be needed to meet global demand and help end the pandemic, raising concern that studies that still need to sign up thousands of volunteers could run short if people wait for an already OK’d option instead.

“We still need volunteers,” stressed National Institutes of Health Director Francis Collins, urging Americans to sign up.

Additionally, participants in the Moderna and Pfizer studies who originally got dummy shots would almost certainly be offered the real vaccine if the U.S. Food and Drug Administration allows emergency use. But no one knows how long protection would last, meaning those studies also must continue to track recipients somehow.

“It’s one thing to be effective two months after your last vaccination and another thing to be effective a year” later, said Dr. Jesse Goodman of Georgetown University, a former director of the FDA’s vaccine division. “It’s going to be really important to complete these clinical trials and the trials of the other vaccines so we can make comparisons.”

Meanwhile, a new study says that eight months after infection, most people who have recovered from covid-19 still have enough immune cells to fend off the virus and prevent illness. A slow rate of decline in the short term suggests that these cells may persist in the body for a very, very long time to come.

The research, published online, has not been peer-reviewed nor published in a scientific journal. But it is the most comprehensive and long-ranging study of immune memory to the coronavirus to date.

“That amount of memory would likely prevent the vast majority of people from getting hospitalized disease, severe disease, for many years,” said Shane Crotty, a virologist at the La Jolla Institute of Immunology who co-led the new study.

The findings are likely to come as a relief to experts worried that immunity to the virus might be short-lived, and that vaccines might have to be administered repeatedly to keep the pandemic under control.

The promising Moderna and Pfizer news bodes well for some of their competitors, said Dr. Anthony Fauci, the U.S. government’s top infectious disease expert whose team at the National Institutes of Health helped develop the Moderna candidate.

Those shots target the “spike” protein that studs the surface of the coronavirus, and the early results prove that’s enough to generate “a protective response,” Fauci said. “Conceptually this looks good” for other spike-focused vaccines made in different ways.

The Moderna-National Institutes of Health vaccine and the candidate developed by Pfizer and its German partner BioNTech aren’t made with the coronavirus itself, meaning there’s no chance anyone could catch it from the shots.

Instead, the vaccines are made with a brand-new technology that injects a piece of genetic code for the spike protein. That messenger RNA, or mRNA, instructs the body to make some harmless spike protein, enough to prime the immune system to react if it later encounters the real virus.

There are no licensed mRNA vaccines for people, so scientists had no idea if or how well the covid-19 candidates might work.

Both manufacturers are working to scale up production in factories in the U.S. and Europe. They can’t simply partner with other vaccine companies to take on some of the work because the technology is so different from the way most of today’s shots are made.

“It is not a very easy or quick swap,” said Moderna CEO Stephane Bancel.

A different way to target the spike protein is to use another, harmless virus to carry the spike gene into the body. Once again, the body produces some spike protein and primes the immune system.

Britain’s Oxford University and AstraZeneca are making their version of this “viral vector” vaccine with a cold virus, or adenovirus, that normally infects chimpanzees. Studies of tens of thousands of people are underway in the U.K., U.S. and several other countries.

Johnson & Johnson is using a human adenovirus for its version, and is the only option in advanced U.S. testing aiming to show if a single dose rather than two would be enough.

Novavax makes its vaccine candidate by growing harmless copies of the coronavirus spike protein in the laboratory and packaging them into virus-sized nanoparticles.

Spike-focused vaccines aren’t the only option. Making vaccines by growing a disease-causing virus and then killing it is a tried-and-true approach — it’s the way Jonas Salk’s famed polio shots were made.

China has three so-called inactivated covid-19 vaccine candidates in final testing in several countries, and has allowed emergency use in some people ahead of the results. An Indian company is testing its own inactivated candidate.