Hopes for a return to normal life after the coronavirus hinge on the development of a vaccine. But there’s no guarantee, experts say, that a fully effective COVID-19 vaccine is possible.

That may seem counterintuitive. So many brutal viral diseases have been conquered by vaccination — smallpox, polio, mumps — that the technique seems all but infallible. But not all viral diseases are equally amenable to vaccination. “Some viruses are very easy to make a vaccine for, and some are very complicated,” says Adolfo García-Sastre, director of the Global Health and Emerging Pathogens Institute at the Icahn School of Medicine at Mount Sinai. “It depends on the specific characteristics of how the virus infects.”

Unfortunately, it seems that COVID-19 is on the difficult end of the scale.

A closely related virus of the same family, SARS, circulated in Asia from late 2002 to mid-2003 and killed more than 700 people. “They really are very similar viruses, both virulent and contagious,” says Rachel Roper, a professor of immunology at East Carolina University who took part in efforts to develop a SARS vaccine.

Given the similarities of the diseases, their response to vaccination would likely be close to identical. So it’s troubling that when researchers conducted animal testing on prospective SARS vaccines, they ran into difficulty. The two versions that they tested both successfully triggered the host animal’s immune system to produce antibodies, but neither was very effective at protecting against the illness. “People think, ‘Oh if you make antibodies to it, it’s going to be protective,’” says Roper. “That’s not necessarily true. We were able to induce an immune response, but it wasn’t good enough to really protect against the disease.”

It’s possible, Roper fears, that COVID-19 could be a virus that proves resistant to vaccination. “This may be one,” she says. “If we have one, this is going to be it, I think.” The FDA has never approved a vaccine for humans that is effective against any member of the coronavirus family, which includes SARS, MERS, and several that cause the common cold.

Even if researchers do develop a COVID-19 vaccine that’s effective at protecting animals, that doesn’t necessarily mean it will do the same for people. “One of the things that they say in science is that ‘mice lie, and monkeys don’t tell the truth,’” Roper says. “You can get something that works in mice, you can get something that works in monkeys, and it still might not work in humans.” So any animal tests will have to be followed by trials to demonstrate that the vaccines are safe for people to use, followed by trials to see if they protect against infection.

In a worst-case scenario, a phenomenon called “immune enhancement” can cause vaccines to make the symptoms of infections worse. Instead of preventing the virus from entering healthy cells, the antibodies actually help them to do so. In 2016, after some 800,000 Filipino schoolchildren were given a dengue-fever vaccine called Dengvaxia, officials realized that some of them had been put at increased risk of life-threatening complications. Investigators wound up looking into the deaths of some 600 children who’d taken part.

Back during the SARS outbreak, researchers were unable to test their SARS vaccine candidates for effectiveness in humans. To do so, they would have had to inoculate a population that was exposed to SARS, and the disease was effectively wiped out using public-health measures before that could happen.

That won’t be a problem for COVID-19 vaccine testing, obviously. And given the scale of the efforts underway, it’s quite possible that one or more vaccines will be found that will overcome whatever problems hampered the SARS vaccines. Currently, more than 35 companies and academic institutions around the world are working on COVID-19 vaccines. The first human trials started last month for a vaccine produced by Boston-area biotech firm Moderna Therapeutics. Pennsylvania-based Inovio Pharmaceuticals started testing its candidate vaccine earlier this month, and Novavax, a Maryland company, has said it will start trials in Australia in May.

Should a fully effective vaccine prove unattainable, Roper points out that even an imperfect vaccine, or one that is only fully effective for a short time, would be better than nothing. “Partially effective vaccines can still prevent serious illness and death,” says Roper. “And even though it’s not perfect protection, it does protect from hospitalization and death. It gives your immune system the jump.”

At this point, it’s not a given that even an imperfect vaccine is a slam dunk. The way that the COVID-19 virus behaves out in the wild makes it hard to predict how it will respond to vaccination. In a sense, immunization is a way to let your body think it’s already had the disease by teaching its immune system to make antibodies against the pathogen. A recent study in China, however, found that many patients who actually had the disease showed very low levels of antibodies in their blood after they recovered — and in some cases had none at all. This might indicate that people who recover from the disease or get vaccinated against it might be able to catch it nonetheless. “We just don’t know yet,” Roper says.

Source: https://nymag.com/intelligencer/2020/04/will-there-be-a-coronavirus-vaccine-maybe-not.html

The post We Might Never Get a Good Coronavirus Vaccine first appeared on Garner Ted Armstrong Evangelistic Association.

The World Health Organization on Tuesday said tens of thousands of people are believed to be infected with dengue fever on La Réunion. The island – a French territory – is a popular vacation destination in the Indian Ocean.

Dengue is a set of viruses found in tropical and sub-tropical parts of the world. Humans get dengue from being bitten by mosquitos infected with the virus.

Health officials on the island told the WHO of the disease outbreak in March 2018. About 50,000 probable cases of the disease were reported between 2018 and April of this year. That includes 22,000 so far in 2019, the health agency said in a statement.

The WHO described the rise of confirmed and probable cases reported last year as unprecedented.

There is no treatment. But with early discovery and good medical care, fewer than one percent of people infected die from the disease.

The WHO said 14 people have died in the Réunion outbreak since 2018. The territory has a population of 866,500.

Around the world, the number of dengue cases dropped from 2017 to 2018. But there has been a huge increase in 2019, especially in Vietnam, Australia, Cambodia, China, Laos, Malaysia, the Philippines and Singapore.

More about dengue

About one in four people infected with dengue will get sick. Of those who do get sick, the symptoms can be mild to severe.

Severe dengue can be deadly and often requires hospitalization. Only a small percentage of people get severe dengue. Mild dengue can be mistaken for other sicknesses, such as influenza.

Symptoms often begin four to seven days after being bitten and commonly last two days to one week. They can include high fever, severe headaches, fatigue, vomiting, and, in severe cases, bleeding.

The first dengue vaccine, Dengvaxia, was approved in 2015 for use in Mexico, Brazil and the Philippines. Several other countries followed in 2016.

The U.S. Food and Drug Administration approved Dengvaxia in 2019. The WHO says the vaccine should not be given to people who have not had an earlier dengue infection.

The World Health Organization notes that dengue fever is now common in over 100 countries. Forty percent of the world’s population lives in an area at risk for dengue.

I’m Caty Weaver.

Tom Miles wrote this report for Reuters news agency. Alice Bryant adapted it for Learning English with additional information from WHO and the Centers for Disease Control and Prevention. Ashley Thompson was the editor.

Words in This Story

destination – n. a place to which a person is going or something is being sent

tropical – adj. of or relating to the part of the world that is near the equator where the weather is very warm

mosquito – n. a small flying insect that bites the skin of people and animals and sucks their blood

unprecedented – adj. not done or experienced before

symptom – n. a change in the body or mind which indicates that a disease is present

mild – adj. not harsh or severe

vomiting – gerund. the act of food or liquid that is in your stomach coming out through your mouth because you are sick (verb: vomit)

Source: https://learningenglish.voanews.com/a/who-dengue-fever-numbers-rise-on-la-r%C3%A9union-/4926841.html

The post WHO: Dengue Fever Numbers Rise on La Réunion (now common in 100 countries) first appeared on Garner Ted Armstrong Evangelistic Association.