President Donald Trump's order directing Americans to receive separate measles, mumps and rubella vaccines faces an immediate obstacle: none of the individual shots are licensed in the United States ‌and experts say it could take years before any become available, if they ever do.

An experimental blood test for detecting colorectal cancer also shows promise for preventing it, researchers say.

Several blood tests are already commercially available for colorectal cancer screening, but the new test is also highly sensitive for precancerous polyps known as advanced adenomas. Removing those polyps can prevent the cancer from developing.

Testing the assay in more than 1,500 adults participating in colonoscopy screening programs in China, Japan, and Spain, they found it detected 92% of stage I, II, or III colorectal cancers and 81% of advanced adenomas, according to a report in The Lancet Gastroenterology & Hepatology.

The test was also 85% accurate at identifying people without precancerous lesions in the colon.

“Developing an acceptable, feasible, non-invasive test that can accurately detect colorectal precancerous lesions could become an extremely valuable tool for preventing, rather than only detecting colorectal cancer,” researchers not involved in the study wrote in an editorial.

Because it can distinguish between low-risk adenomas, high-risk adenomas, and cancers, the blood test could potentially be used to risk-stratify patients who require urgent colonoscopy, those who might still require a colonoscopy to remove advanced adenomas and thereby prevent colorectal cancer, and those who might not need a colonoscopy, the researchers said.

Doctors still recommend colonoscopy as the gold-standard method for colorectal cancer screening, with stool tests and blood tests advised only for patients who won’t or can’t comply.

Positive blood tests still require follow-up colonoscopies, but patients are more likely to comply in those cases, earlier studies have shown.

Researchers say larger-scale trials of the new blood test are still needed, particularly because while it found worrisome polyps, which are small bumps or overgrowths, it was less successful at identifying so-called sessile, or flat, areas of concern.

A flavoring chemical frequently used at high concentrations in e-cigarettes may disrupt the normal development of embryos in pregnant women who vape, laboratory experiments suggest.

The researchers investigated the effects of the flavoring vanillin in test tubes because it would be unethical to test the chemical on human embryos in pregnant women.

The human embryonic stem cells in the experiments, similar to those present in human embryos at three weeks of pregnancy, had the potential to differentiate into any type of cell.

When the researchers exposed the cells to microscopic amounts of vanillin, they found that so-called micromolar concentrations tended to kill the cells, while nanomolar concentrations caused the cells to lose their ability to develop into all cell types.

“These changes are potentially very serious and could prevent normal development of embryos,” study leader Prue Talbot of the University of California Riverside said in a statement.

Embryonic cells are known to have a protein called TRPV4 on their surfaces that binds with vanillin. When the researchers blocked the actions of that protein, the effect of vanillin on the stem cells was also blocked, leading them to conclude that TRPV4 explains the flavor's effects on the cells.

The researchers warn that results in test tubes do not prove the same effects would be seen in women and their embryos.

Still, the study may help to explain why vaping has been linked to women having difficulty conceiving and to miscarriages, they said in a report published in Human Reproduction.

“Women do not necessarily know the chemicals in vape products,” Talbot said. “Our findings suggest they should be cautious and advised by physicians not to vape during pregnancy, especially if they are having trouble conceiving or experience miscarriages."