[Local Medical]Three types of people who are prone to severe illness from influenza should get vaccinated to prevent it

Text◆Yang Qianni

Influenza is a highly contagious acute respiratory disease.

There are types A, B and C of influenza viruses. Types A and B are mainly prevalent in the population and cause disease.

Because the symptoms are similar, the flu can easily be confused with other respiratory illnesses, such as the common cold.

(Kuala Lumpur News) Dr. Petrick @ Ramesh K. Periyasamy, Director of the Department of Infectious Diseases and Consultant of the Department of Infectious Diseases at the National University Medical Center, pointed out that in fact, influenza (influenza, referred to as influenza) is not as harmless as the public imagines. In addition to possibly causing fever, headache, dry cough, sore throat, nasal congestion, muscle pain or stomach symptoms such as diarrhea, nausea, vomiting, etc.

The virus survives in the air for 2 to 3 hours

Pregnant women, children aged 6 months to 5 years, seniors aged 60 and above, and people with chronic diseases are at higher risk for serious complications, such as meningitis, seizures, myocarditis, aggravated heart disease, and secondary complications. Bacterial pneumonia, etc. “

“In addition, influenza infection during pregnancy may lead to low birth weight, premature birth and increased pregnancy complications.”

“The World Health Organization estimates that

There are 3 million to 5 million severe influenza cases worldwide every year.

and caused approximately 290,000 to 650,000 deaths.

According to a study conducted at two hospitals from July 2018 to February 2019

Influenza surveillance survey conducted by (Selayang Hospital and UM Medical Center),

Among 350 hospitalized patients aged 18 to 80 who presented with acute respiratory symptoms, 14% were diagnosed with influenza cases, with influenza A accounting for 89.8% and influenza B accounting for 10.2%. “

“Current approaches that can reduce seasonal influenza include prevention, symptom management and antiviral treatment. Non-pharmacological interventions can reduce the spread of the virus, including frequent hand washing, self-isolation, wearing a mask and observing cough etiquette. This is because influenza viruses can survive 5 minutes on hands, 24 to 48 hours on hard surfaces and 8 to 12 hours on cloth.”

“Not only that, the influenza virus can survive in the air for at least 2 to 3 hours. Therefore, after being diagnosed, it is best for patients to have less contact with others and wear masks, and at the same time do a good job in environmental cleaning and waste disposal.”

He said that according to the Malaysian Society of Infectious Diseases and Chemotherapy (MSIDC) adult vaccination guidelines, they advocate anyone aged above 50, those aged 18 to 49 with one or more chronic diseases, pregnant women and all healthcare workers to receive the influenza vaccine.

“It is also recommended that family members who are in close contact with high-risk groups, including caregivers of infants under 6 months old, be vaccinated. The probability of household transmission of influenza virus is 30%, especially if there are susceptible people in the household. It is best to maintain physical distance and wear masks at home.”

“However, the vaccination rate in many countries is still very low. This is related to the fact that many people do not pay much attention to influenza, think it is just a common cold, and have insufficient awareness of prevention. In addition, some people feel that the vaccine is not very effective or are worried about side effects, and every year The need for repeated vaccinations and cost are also among the reasons for the low vaccination rate.”

Virus strain mismatch affects efficacy

He said that research by the U.S. Centers for Disease Control and Prevention (CDC) showed that the effectiveness of the seasonal influenza vaccine in 2004-2005 could be as low as 10%, while the effectiveness in 2010-2011 was 60%, which is also the best.

“Why does the protective efficacy of influenza vaccination vary? In addition to suboptimal uptake, there is a mismatch between the protective efficacy of the vaccine and the actual circulating virus strains that year, which will also affect the protective efficacy. In addition, the vaccine The protective effect tends to decrease when type A H3N2 viruses become dominant.”

He said that antiviral treatment mainly helps reduce mortality, hospitalization rates and the duration of symptoms. However, the drug options for treating influenza are limited and can be divided into three categories: M2 protein inhibitor (M2PI), Neuraminidase Inhibitor (NAI), and the newly developed Cap-Dependent Endonuclease Inhibitor (CDEI).

“Simply put, the life cycle of an influenza virus goes through several stages: attachment to host cells, entry into the cell through membrane fusion, viral genome replication in the nucleus, protein synthesis, and finally the newly formed virus through budding. The virus is released.”

“Adamantanes such as amantadine and rimantadine are drugs used to inhibit early viral replication by blocking the M2 protein ion channel (matrix 2 ion channel protein) of influenza A virus to prevent the migration of the viral genome to the nucleus. However, due to widespread drug resistance, these drugs are no longer used in clinical treatment.”

He said that NAI drugs such as oseltamivir, peramivir, zanamivir, etc. inhibit the neuraminidase activity on the surface of the virus, thereby blocking the detachment and release of newly formed virus particles from host cells.

The best treatment time is 48 hours after onset of illness

“The CAP cap structure-dependent endonuclease (CDE) in influenza viruses is critical for the replication of influenza viruses. Therefore, baloxavir marboxil, a CDE inhibitor, is the first to be approved by the U.S. Food and Drug Administration in the past 20 years. (FDA) approves new mechanism of action drug for treating influenza.”

“In comparison, currently available drugs interfere with the virus’s ability to spread in the human body, while new drugs interfere with the influenza virus’s ability to reproduce.”

In any case, he pointed out, the limitations of anti-flu viral drugs include varying efficacy (60% to 90%), partly because the virus has developed resistance to some older drugs, and partly because many people think that influenza is not a big problem. Waiting to see a doctor three or four days after the onset of illness will reduce the effectiveness of treatment. Regardless of the antiviral drug used, the best time to treat influenza is within 48 hours of onset.

New medicine only requires 1 dose Self-discontinuation leads to drug resistance

Compared with the traditional drug oseltamivir, which needs to be taken twice a day for 5 days, the advantage of baloxavir marboxil is that it only needs to be taken in one dose.

In the past, many patients often stopped taking medications on their own after feeling symptoms improved, which also led to problems with drug resistance and treatment efficacy.

How effective and safe is baloxavir marboxil compared to older drugs?

Patrick pointed out that in a multi-center, randomized, double-blind, placebo- and oseltamivir-controlled Phase III CAPSTONE-1 study, 1,436 patients with uncomplicated influenza received 5 days of treatment and 17 days of follow-up. track.

“The primary endpoint of this clinical study is Time To Alleviation of Symptoms (TTAS), followed by observing how long the virus remains in the body and fever reduction time, as well as understanding the safety and side effects of the drug.”

Reduces fever faster than placebo

“Patients aged 20 to 64 years were randomized in a 2:2:1 ratio to receive a single dose of 40 mg (body weight less than 80 kg) or 80 mg (body weight 80 kg and above) of baloxavir marboxil on the first day for 5 consecutive days. Patients aged 12 to 19 years were randomized to receive a single oral dose of baloxavir marboxil or placebo in a 2:1 ratio based on body weight.”

He said that the study found that baloxavir marboxil significantly improved TTAS compared with placebo. It takes an average of 80.2 hours to relieve symptoms without taking any drugs, while baloxavir marboxil takes 53.7 hours. Patients can save more than 1 day and return to work faster. This effect is similar to oseltamivir. In addition, baloxavir marboxil reduced fever significantly faster (24.5 hours) compared with 42 hours for placebo.

Being asymptomatic does not mean that there is no virus in the body

“We know that even if there are no symptoms or symptoms have been relieved, it does not mean that there is no virus in the body and it is still possible to infect others. Studies have found that the use of baloxavir marboxil can significantly reduce viral titres. Within 1 day of administration, patients taking oseltamivir 90% were still influenza positive, while only 50% of patients taking baloxavir marboxil had detectable influenza virus.”

“Not only that, baloxavir marboxil also significantly shortened the viral shedding period (viral shedding), that is, the ability of the virus to spread from one person to another, from 4 days to 1 day, while oseltamivir required 3 days, which was obviously not so fast. Inhibitory power. This is very critical to limiting the spread of the virus, and we think this is related to its unique mechanism of action.”

He said baloxavir marboxil also showed good tolerability, with an overall adverse event rate of 20.7%, lower than the 24.6% for placebo and 24.8% for oseltamivir.

“In terms of safety, baloxavir marboxil is also comparable to placebo. Common side effects are diarrhea, bronchitis, nasopharyngitis, nausea and sinusitis.”

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