The US Food and Drug Administration (FDA) on Wednesday, May 3, 2023, approved the world’s first respiratory syncytial virus vaccine. The vaccine, called Arexvy, is manufactured by British pharmaceutical company GSK, and has been approved for use in individuals aged 60 years and above in the United States. Arexvy is an adjuvanted respiratory syncytial virus vaccine, which means that it has an adjuvant, or an ingredient that helps create a stronger immune response to vaccination.
The aim of the vaccine is to prevent lower respiratory tract disease caused by respiratory syncytial virus in older adults, the FDA said in a statement.
The vaccine is planned to be launched in the US before the 2023/2024 respiratory syncytial virus season, the period when outbreaks of the virus tend to occur, and people are at increased risk of severe or life-threatening infections caused by the pathogen. In most regions of the US, respiratory syncytial virus season begins in the fall and peaks during winter, according to the Centers for Disease Control and Prevention.
All about respiratory syncytial virus
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Respiratory syncytial virus is a highly contagious respiratory virus that causes symptoms such as cough, sneezing, fever, wheezing, runny nose and a decreased appetite, according to the CDC. It usually takes a week or two for most people to recover from respiratory syncytial virus infection. However, in some cases, the virus can cause severe infection, especially in children and older adults.
In the US, respiratory syncytial virus is the most common cause of bronchiolitis, or inflammation of the small airways in the lungs, and pneumonia, or infection of the lungs, in children aged less than a year.
It is a common cause of lower respiratory tract disease in older adults, according to the FDA. Lower respiratory tract disease can affect the lungs and cause life-threatening pneumonia and bronchiolitis.
How many people does the virus affect worldwide?
The virus has infected nearly all children in the US by the time they are two years of age, according to the US National Institutes of Health (NIH). Children with chronic lung disease or congenital heart disease are more susceptible to respiratory syncytial virus infection.
All individuals with chronic medical conditions such as heart or lung disease, people with weakened immune systems, and older adults, especially those aged 65 years and above, are at higher risk of having a severe respiratory syncytial virus infection, compared to others.
The virus causes approximately 58,000 hospitalisations among children aged less than five years in the US annually. An estimated 64 million people worldwide are affected by respiratory syncytial virus infection. The virus results in about 1,60,000 deaths each year worldwide.
How is the virus spread?
Respiratory syncytial virus is air-borne as well as fomite-borne. It is transmitted through coughing and sneezing, through direct contact with an infected individual, or by touching objects with the virus on it.
What are the treatments for infection with respiratory syncytial virus?
Treatments for respiratory syncytial virus infections include over-the-counter pain relievers that can remove the pain and fever caused by the virus. The NIH states that aspirin should not be given to children, and cough medicine must not be given to children below four years of age.
People infected with respiratory syncytial virus must stay hydrated, and in case of severe infection, should get hospitalised and take oxygen support.
According to GSK, respiratory syncytial virus infection can exacerbate comorbidities such as chronic obstructive pulmonary disease (COPD), asthma, and chronic heart failure, and can even lead to death.
All about Arexvy
Arexvy contains a recombinant subunit prefusion respiratory syncytial virus F glycoprotein antigen (RSVPreF3) combined with GSK’s proprietary AS01E adjuvant, the London-based pharmaceutical firm said in a statement. Recombinant subunit vaccines are the ones manufactured by inserting defined protein antigens into other cells, such as yeast cells, in order to produce a large number of subunits.
The antigens are usually genetic codes of the targeted virus, and are purified, which means they will not be pathogenic to the person receiving the vaccine, and will instead illicit an immune response.
Prefusion stabilisation is a technique that increases the recombinant expression of viral fusion glycoproteins, by preventing misfolding, according to a study published in the journal Science.
Viral glycoproteins are integral parts of enveloped viruses, and fusion (F) glycoprotein is an important part of the respiratory syncytial virus. The F glycoprotein mediates fusion of the viral and cell membranes to allow the virus to enter the host cell and initiate a new infectious cell. Therefore, using this antigen inside the respiratory syncytial virus vaccine will allow the immune system of the host organism to produce antibodies against the F glycoprotein, and allow them to neutralise virus particles in the wake of a future infection.
Arexvy will be used to prevent lower respiratory tract infections caused by respiratory syncytial virus in US individuals aged 60 years and above. The vaccine is currently not approved anywhere outside the US, GSK said in the statement.
Safety and effectiveness of Arexvy
A randomised, placebo-controlled clinical study is being conducted in the US and internationally in individuals aged 60 years and above. The FDA has analysed the data from the clinical trial, based on which the safety and effectiveness of a single dose of Arexvy has been decided.
While the aim of the main clinical study was to assess the safety and effectiveness of a single dose, participants will remain in the study through three respiratory syncytial virus seasons to assess the duration of effectiveness and the safety and effectiveness of a second dose, or repeat vaccination, according to the FDA.
Approximately 12,500 participants have received Arexvy, and 12,500 participants have received a placebo, as part of the study.
The study found that Arexvy significantly reduced the risk of developing respiratory syncytial virus-associated lower respiratory tract disease by 82.6 per cent, and decreased the risk of developing severe respiratory syncytial virus-associated lower respiratory tract disease by 94.1 per cent, according to the FDA.
This means that the overall efficacy of Arexvy is 82.6 per cent. In older adults with at least one underlying medical condition, such as conditions affecting the cardiovascular system, respiratory system, endocrine system or metabolism, the efficacy of Arexvy was 94.6 per cent, GSK said in a statement.
Arexvy was generally well tolerated with an acceptable safety profile, according to GSK.
Side effects of Arexvy
Injection site pain, myalgia, or pain in muscles, arthralgia, or pain in joints, fatigue and headache were the most frequently observed adverse events. However, they were generally mild to moderate.
A subset of these clinical trial participants reported side effects such as fatigue, headache, injection site pain, muscle pain, and joint pain or stiffness.
As many as 10 participants who received Arexvy reported atrial fibrillation, or an irregular and rapid heart rhythm that can lead to blood clots in the heart, within 30 days of vaccination.
Two other studies were conducted, as part of which approximately 25,000 participants 60 years of age and above received Arexvy.
In one of the studies, some of the participants received Arexvy as well as an FDA-approved influenza vaccine. Among these participants, two individuals developed acute disseminated encephalomyelitis (ADEM), a neurological disorder in which inflammation of the brain and spinal cord occurs. This damages the myelin, the white protective coating of nerves.
The participants developed ADEM seven days after receiving Arexvy, and 22 days after receiving the influenza vaccine. One of them has died.
In the other study, a participant developed Guillain-Barré syndrome nine days after receiving Arexvy.
Guillain-Barré syndrome is a rare condition in which a person’s immune system attacks the peripheral nerves, the network of nerves located outside the brain and spinal cord, and is characterised by weakness, sensation changes, tingling in the feet and hands, difficulty with eye muscles, vision, trouble speaking, and coordination problems, among others, according to the NIH.
What is next?
According to GSK, a clinical trial to assess the effectiveness of vaccination against respiratory syncytial virus in adults aged 50 to 59 years is fully recruited, and its results are expected in 2023.
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