Sunday January 26, 2020

U.S. Measles Outbreak Raises Concerns About Immunity in Adults

This has occurred even in adults with two documented doses of the vaccine, said Dr. Michael Phillips, chief epidemiologist at NYU Langone Health, which serves parts of New York City, a hot spot in the U.S. outbreak.

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People vaccinated in the United States since 1989 would most likely have received two doses of the combined measles, mumps and rubella (MMR) shot under federal guidelines, and that is still considered the standard for protection. Pixabay

Adults in the United States who were vaccinated against measles decades ago may need a new dose depending on when they received the shot and their exposure risk, according to public health experts battling the nation’s largest outbreak since the virus was deemed eliminated in 2000.

Up to 10 percent of the 695 confirmed measles cases in the current outbreak occurred in people who received one or two doses of the vaccine, according to the U.S. Centers for Disease Control and Prevention.

The figure illustrates what can happen when a large number of individuals, even those who have been vaccinated, are exposed to the measles. CDC recommends that people who are living in or traveling to outbreak areas should check their vaccination status and consider getting a new dose.

Dr. Allison Bartlett, an infectious disease expert at the University of Chicago Medicine, said the “continued vulnerability to infection” is why high-risk adults such as healthcare workers are routinely advised to get a second dose of the measles vaccine if they have not had one.

But knowing your vaccination status can be tricky, experts said.

“It’s complicated and often futile because it’s very difficult to resurrect those old records,” said Dr. William Schaffner, an infectious disease expert at Vanderbilt University Medical Center.

measles
Los Angeles County Department of Public Health experts, Muntu Davis, Health Officer, left, and Director Dr. Barbara Ferrer answer questions regarding the measles response and the quarantine orders during a news conference in Los Angeles Friday, April 26, 2019. VOA

People vaccinated in the United States since 1989 would most likely have received two doses of the combined measles, mumps and rubella (MMR) shot under federal guidelines, and that is still considered the standard for protection.

Anyone vaccinated between 1963 and 1989 would likely have received only one dose, with many people immunized in the earlier years receiving an inactivated version of the virus. Americans born before 1957 are considered immune as they would have been exposed to the virus directly in an outbreak.

Merck & Co Inc is the sole U.S. provider of the MMR vaccine. The company said in a statement that it has “taken steps to increase U.S. supply” of the vaccine due to the current outbreak.

HIGHLY CONTAGIOUS

The measles virus is highly contagious and can cause blindness, deafness, brain damage or death. It is currently spreading in outbreaks in many parts of the world.

According to the World Health Organization, 95 percent of a population needs to be vaccinated to provide “herd immunity,” a form of indirect protection that prevents infection in people too young or sick to be vaccinated. U.S. public health officials have blamed the current outbreak in part on rising rates of vaccine skepticism that have reduced measles immunity in certain communities.

For travelers to outbreak areas abroad, the CDC recommends adults consider getting another dose of MMR unless they have proof of receiving two prior doses, take a blood test showing immunity, or were born before 1957.

In general, the CDC says two doses of the measles vaccine should provide 97 percent protection; one dose should offer 93 percent protection. However, immunity can wane over time.

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Rapid blood tests are available that can detect whether a person is immune based on the level of measles antibodies, but the tests are not 100 percent reliable. Pixabay

This has occurred even in adults with two documented doses of the vaccine, said Dr. Michael Phillips, chief epidemiologist at NYU Langone Health, which serves parts of New York City, a hot spot in the U.S. outbreak.

He said in kids, “the vaccine is really effective,” but in some adults, memory T-cells, which recognize and attack germs, do not fight the virus as effectively as they once did.

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Rapid blood tests are available that can detect whether a person is immune based on the level of measles antibodies, but the tests are not 100 percent reliable.

Adults who have any doubt about their immunity should get another dose, Schaffner said: “It’s safe. There’s no downside risk. Just roll up your sleeve.” (VOA)

Next Story

Experimental Vaccine for Swine Fever Virus Shows Promise

When they deleted this gene, ASFV-G was completely attenuated

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Pigs, Swine Fever, Asia
Almost 5 million pigs in Asia have now died or been culled because of the spread of African swine fever over the past year, the United Nations Food and Agriculture Organisation said on Friday, warning Asian nations to keep strict control measures in place. Pixabay

Researchers have developed a vaccine against African swine fever that appears to be far more effective than previously developed vaccines.

Currently, there is no commercially available vaccine against African swine fever, which has been devastating the swine industry in Eastern Europe and Southeast Asia.

African swine fever virus (ASFV) is highly contagious and often lethal to domestic and wild pigs, according to the the study, published in the Journal of Virology.

“This new experimental ASFV vaccine shows promise, and offers complete protection against the current strain currently producing outbreaks throughout Eastern Europe and Asia,” said study researcher Douglas P Gladue from Plum Island Animal Disease Center, Agricultural Research Service, US Department of Agriculture.

The research was motivated by the 2007 outbreak of African swine fever in the Republic of Georgia.

“This was the first outbreak in recent history outside of Africa and Sardinia–where swine fever is endemic–and this particular strain has been highly lethal and highly contagious, spreading quickly to neighboring countries,” Gladue said.

“This is also a new strain of the virus, now known as ASFV-G (the G stands for Georgia),” Gladue added.

chinese pork, african swine fever
Pigs stand in a barn at a pig farm in Jiangjiaqiao village in northern China’s Hebei province on May 8, 2019. Pork lovers worldwide are wincing at prices that have jumped by up to 40 percent as China’s struggle to stamp out African swine fever in its vast pig herds sends shockwaves through global meat markets. RFA

For the findings, researchers set out to develop a vaccine. Part of the process of developing whole virus vaccines involves deleting virulence genes from the virus.

But when the researchers deleted genes similar to those that had been deleted in older ASFV strains to attenuate them, “it became clear that ASFV-G was much more virulent” than the other, historical isolates, because it retained a higher level of virulence, said Gladue.

The researchers then realised they needed a different genetic target in order to attenuate ASFV-G.

They used a predictive methodology called a computational pipeline to predict the roles of proteins on the virus. The computational pipeline predicted that a protein called I177l could interfere with the immune system of the pig.

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When they deleted this gene, ASFV-G was completely attenuated.

In the study, both low and high doses of the vaccine were 100 per cent effective against the virus when the pigs were challenged 28 days post-inoculation, the researchers said. (IANS)