Trivalent vs. quadrivalent

Flu vaccinations are broken into two major types: trivalent and quadrivalent. Trivalent vaccines, or the traditional flu vaccines, have been around longer. They include protection against two type A flu viruses, H3N2 and H1N1, and one type B virus. For many years, however, two type B strains have circulated in the U.S., prompting the creation of quadrivalent vaccines, which protect against, as the name implies, four strains of flu. Like trivalent vaccines, quadrivalent vaccines protect against the two type A viruses. But unlike trivalents, quadrivalents protect against two type B strains, rather than protecting against the one that’s predicted to be circulating in a given year.

“The truth is, it’s very much like flipping a coin,” said Dr. Pedro Piedra, professor of molecular virology and microbiology and pediatrics at Baylor College of Medicine in Houston, said of predicting which B strain to include in trivalent vaccines.

For that reason, Piedra and others recommend people ask their doctors for quadrivalent vaccines. That said, if your doctor’s office only has the trivalent version, it’s more important to get the shot than hesitate.

“The main thing is to get a flu shot,” said Dr. Ann Thomas, a public health physician with the Oregon Health Authority.

With some indications that this year’s flu season could hit older adults particularly hard, doctors are encouraging people to not only get their flu vaccinations, but pay careful attention to which vaccination they get.

The severity of a flu season is notoriously difficult to predict, but experts in the U.S. attempt to do so by observing what happens in the Southern Hemisphere, which experiences its flu season during the summer in the U.S. The dominant virus in circulation there during the recently-ended flu season was the H3N2 subtype, which historically tends to cause the greatest number of deaths, particularly in older adults, said Dr. Pedro Piedra, professor of molecular virology and microbiology, and pediatrics at Baylor College of Medicine in Houston. That’s also the strain that circulated in the U.S. — albeit at very low levels — during the summer, he said.

“You kind of put both of those together and it suggests that we’re likely to have an H3N2-dominant year,” Piedra said.

As people age, their immune systems wear down. When that happens, they don’t produce as much antibody in response to traditional flu vaccines in comparison to younger people.

There are two shots available in the U.S. specifically for people over 65. They work two different ways. One, Fluzone, contains four times the amount of antigen contained in traditional flu shots. The other, Fluad, approved for use in the U.S. in November 2015, contains an ingredient called an adjuvant that enhances immune response.

Currently, there is no research that compares Fluad and Fluzone against one another. Researchers at Duke and Boston universities are currently conducting a study that will compare the vaccines in terms of effectiveness and adverse outcomes.

But until such science is published, doctors, including those from the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices, don’t recommend one over the other.

Doctor’s offices typically stock either Fluzone or Fluad, but not both, so Piedra recommends going with either one. If you’re over 65, just make sure you’re getting one of the high-dose vaccines, he said.

Since both vaccines increase patients’ immune response beyond that of traditional flu vaccines, patients can expect a bit more of a reaction at the injection site, such as pain, redness or swelling, but that should resolve itself in a day or two, said Dr. Ann Thomas, a public health physician with the Oregon Health Authority.

The high-dose vaccines are by no means perfect. A 2013 study in the journal Vaccine compared the effectiveness of Fluad to a traditional flu vaccine on 282 elderly subjects and found the former was about 60 percent protective, compared to the traditional vaccine, which the study found offered no protection.

While not a panacea, the study authors concluded it offers significantly better protection against hospitalization and death.

Older adults who get Fluad or Fluzone might still get the flu, but in addition to lowering the risk of contracting the virus, the vaccines also tend to protect against the more severe forms of the disease, Piedra said.

“And the most severe disease is death,” he said, “and so even though it’s not a perfect vaccine, it is very easy, it’s inexpensive, it’s very safe and the best way that we have for protecting our population.”

The Oregon Health Authority keeps data on the percent of health care workers who receive flu vaccinations. Skilled nursing facilities, more commonly known as nursing homes, tend to have the lowest rate of vaccinations, although those rates have been slowly increasing over the years. During the 2015-16 flu season, 60 percent of workers at skilled nursing facilities were vaccinated against the flu, compared with 47 percent during the 2011-12 season.

Flu vaccination rates were low at some of those facilities in Central Oregon. At Bend Transitional Care, for example, 41 percent of 95 eligible workers received a flu vaccination, a nearly 50 percent drop from the previous season. A representative there did not return a request for comment.

At Regency Care of Central Oregon, 60 percent of 48 eligible workers received the vaccinations, a 55 percent increase from the previous season. A representative there also did not return a request for comment.

Susan Peschin, CEO of the Alliance for Aging Research, a nonprofit dedicated to accelerating scientific discoveries around aging and health, said those numbers are significant, as older residents of long-term care settings like nursing homes are vulnerable to getting the flu and suffering complications.

Peschin recommends skilled nursing facilities provide the vaccinations to their employees free of charge.

“It’s not just to protect the residents; it’s to protect you as well,” she said. “It’s to make sure you can get up and go to work and get your paycheck, and it’s to protect your families when you get home if there are residents that have the flu. It’s good for everybody.”

The state doesn’t provide data on vaccination rates among workers at other types of facilities for older adults, such as residential care facilities.

Mount Bachelor Memory Care, a residential care facility in Bend, offers free flu vaccinations for all residents and employees. Staff members who decline the vaccination must wear masks during flu season, said Mallory DaCosta, Mount Bachelor Memory Care’s executive director. In rare cases, residents’ family members decline on their behalf.

DaCosta said she notices a big difference in residents’ health between years when the vaccine matches the dominant flu strain in circulation and years when it doesn’t. In the latter years, pneumonia is more common.

“It was funny because I was always kind of a flu-shot skeptic myself,” she said, “and then when I saw the difference in how many people were sick when we didn’t have the right strain … you could definitely see the difference in how many people were more susceptible.”

—Reporter: 541-383-0304,

tbannow@bendbulletin.com

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