RSV vaccination: Who and when

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Reference: April 2025 | Issue 4 | Vol 11 | Page 23

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Vaccination is a cornerstone of public health and disease prevention. It is one of the most impactful public health measures, responsible for significantly reducing the prevalence of numerous infectious diseases worldwide. Diseases that once caused considerable morbidity and mortality have now been nearly eradicated.

Vaccination is defined as the administration of a preparation that enhances an individual’s immunity to a pathogen. The efficacy of vaccinations can vary between conditions. For instance, the measles vaccine has a high level of efficacy, while the influenza vaccine demonstrates seasonally variable efficacy, ranging from 40 to 90 per cent.

Respiratory syncytial virus (RSV) is a respiratory virus that primarily affects vulnerable populations such as children, elderly people, and immunocompromised individuals. RSV infection often presents with upper respiratory symptoms but can sometimes involve the lower respiratory tract.

Vaccines

Vaccination involves the administration of a compound that enhances an individual’s immunity to a particular disease. Vaccines contain a form of the pathogen, which could be a weakened or inactivated form, an inactivated toxin, or a protein from the pathogen’s surface. By introducing this form of the pathogen, the immune system recognises the antigen as foreign, initiating the production of antibodies and memory T-lymphocytes.

This immunological response enables a more rapid and robust defence if the body encounters the pathogen in the future. Without vaccination, the first exposure to the pathogen could cause significant harm or even death before the immune system provides a sufficient response.¹

Recent advancements in vaccine technology have revolutionised disease prevention strategies. For example, the introduction of mRNA vaccines for Covid-19 in recent years has demonstrated the potential for rapid development against emerging pathogens, including RSV. Additionally, newer vaccine platforms may facilitate multi-disease vaccination, offering greater protection in fewer doses and making mass immunisation efforts more feasible and cost-effective.^1,2

Vaccines can be classified into several types, including live attenuated vaccines, inactivated vaccines, mRNA vaccines, subunit vaccines, and toxoid vaccines.

Live attenuated vaccines contain a weakened version of the pathogen. They mimic a natural infection and can therefore create strong, long-lasting immunity. However, live vaccines may not be suitable for severely immunocompromised individuals. An example of a live attenuated vaccine is the mumps, measles, and rubella (MMR) vaccine.³

Inactivated vaccines use the ‘killed’ version of the disease-causing pathogen which is unable to reproduce inside the host and therefore cannot revert to a harmful state or transmit the disease to others. However, they can be less effective at inducing a long-lasting immune response and often require formulation with an adjuvant or multiple doses. Hepatitis A vaccine and polio vaccine are examples of inactivated vaccines.³

Toxoid vaccines use inactivated toxins produced by the pathogen to create immunity to the toxin rather than the entire pathogen. This type of vaccine often requires booster shots to maintain longer-term immunity. The tetanus vaccine is an example of a toxoid vaccine.³

Subunit vaccines use specific components of the pathogen, such as a protein, sugar, or capsid. By incorporating only specific pieces of the virus, these vaccines elicit a strong immune response to key components of the pathogen.

They also may require booster shots to provide ongoing protection against disease, but are generally safe for most individuals, including those with weakened immune systems and chronic health conditions. The hepatitis B vaccine, human papillomavirus (HPV), pneumococcal, and meningococcal vaccines are all examples of subunit vaccines.³

mRNA vaccines introduce genetic material that encodes a protein, prompting the immune system to produce antibodies. They pose no risk of causing disease as they do not contain a live pathogen. The Covid-19 vaccine is an example of a mRNA vaccine.³

Childhood immunisation

Vaccinations are indicated for preventing a wide range of bacterial and viral infections and their sequalae. Vaccination recommendations may vary by region, reflecting differences in disease exposure and prevalence. The current childhood immunisation schedule recommended by the HSE is as follows:⁴

• 2 months – 6-in-1 vaccine (diphtheria, haemophilus influenzae type b (Hib), hepatitis B, acellular pertussis, inactivated polio, tetanus), Men B (meningococcal B) recombinant vaccine, pneumococcal conjugate vaccine (PCV), rotavirus vaccine.
• 4 months – 6-in-1 vaccine, Men B vaccine, rotavirus vaccine.
• 6 months – 6-in-1 vaccine, PCV.
• 12 months – MMR vaccine, Men B vaccine, varicella (chickenpox) vaccine.
• 13 months – 6-in-1 vaccine, PCV,
  Men C conjugate vaccine.
• Junior infants – 4-in-1 vaccine (diphtheria, tetanus, pertussis, polio), MMR vaccine.
• First year (secondary school) – HPV (human papillomavirus) vaccine, Tdap (low-dose diphtheria, tetanus, and acellular pertussis) vaccine, meningococcal A, C, W, Y conjugate vaccine.⁴

The live attenuated influenza vaccine is recommended for individuals aged two to 17 years, while the quadrivalent inactivated influenza vaccine is recommended for individuals at risk, including those aged 60 years and older, individuals with chronic health conditions, pregnant women, and healthcare workers. Starting from 16 weeks, pregnant women should receive the Tdap vaccine. Covid-19 vaccination is recommended for individuals aged six months and older.

The pneumococcal polysaccharide vaccine is recommended for individuals aged 65 years and older, as well as individuals at risk aged two years and older. Additional vaccines, such as tetanus boosters (every 10 years if required), hepatitis vaccines, rabies vaccines, and yellow fever vaccines, may be necessary depending on an individual’s occupation or travel plans.^1,4

Contraindications

Contraindications to vaccination are rare but can vary between vaccines. The primary contraindication to any vaccine is a documented allergy to the vaccine or one of its components. Severely immunocompromised individuals should generally avoid live attenuated vaccines, as these vaccines may pose a risk of causing infection.

Pregnant women are typically advised against receiving live attenuated vaccines unless absolutely necessary, due to the potential risk of transmitting the pathogen to the fetus. Vaccination should also be deferred in individuals experiencing an acute febrile illness, as it may complicate the diagnosis of the underlying condition. Vaccination is recommended once the febrile illness has resolved.¹

Adverse effects

All vaccines carry a risk of adverse effects, but these are typically mild and self-limiting. Local effects, including pain, redness, and swelling at the site of injection are very common. Localised muscle soreness may also occur. Generalised symptoms are also common and are due to the immune response to the vaccine. These symptoms usually resolve within a few days and include fever, fatigue, and myalgia.

Irritability in young children is also frequently observed. More serious complications are also possible but are extremely rare. Anaphylaxis may occur in response to a vaccine or one of the component ingredients. Guillain-Barre Syndrome is a very rare but serious adverse effect that affects the peripheral nervous system, potentially causing muscle weakness and paralysis.¹

Barriers

Vaccination is a cornerstone of public health and disease prevention, yet anti-vaccination movements and vaccine hesitancy have contributed to declining vaccination rates in some populations. This decline has resulted in the resurgence of previously well-controlled diseases, posing significant risks to public health.

Despite the proven benefits of vaccines, many barriers to vaccination still exist. There is misinformation about the safety and efficacy that contributes to a decline in confidence in vaccines. There are some misconceptions regarding vaccinations, where individuals may perceive themselves as healthy and view vaccination as unnecessary.

Furthermore, individuals may have a fear of experiencing pain or adverse effects from vaccination, or they have had a previous negative experience post-vaccination. Finally, limited primary care resources can hinder access to vaccines. Long waiting times, inconvenient clinic locations, and insufficient healthcare infrastructure contribute to reduced vaccination uptake.⁵

Sustained and strategic efforts are essential to address these challenges and improve vaccination rates. It is vital to reduce vaccine hesitancy through clear, evidence-based communication. Providing accurate information about the safety, efficacy and necessity of vaccines is critical to building patient trust and dispelling myths.

RSV

RSV is one of the most common respiratory viruses that infect children worldwide and is increasingly an important virus in adults, particularly the elderly. RSV is a single-stranded, negative-strand RNA virus. It is highly contagious, causing outbreaks through community and hospital transmission.

Some infants and patients with weakened immune systems may continue to spread the virus, even after symptoms resolve, for as long as four weeks. After inoculation into the nasopharyngeal mucosa or conjunctival mucosa, RSV quickly spreads into the respiratory tract, targeting ciliated epithelial cells. There is a lack of long-term immunity after infection, making reinfection possible.

RSV primarily affects infants and young children, with approximately 90 per cent of children infected within the first two years of life. Older adults and immunocompromised individuals are also at higher risk due to declining immunity.²

The most common clinical presentation of RSV infection is an upper respiratory tract infection. If limited to the upper respiratory tract, symptoms tend to be milder and include rhinorrhoea, cough, sneezing, mild fever, and myalgia. However, RSV often progresses to bronchiolitis. This progression is more common in younger children and those at a higher risk of complications.

Symptoms of bronchiolitis can include wheezing, tachypnoea, and prolonged expiration. In some cases, this can further progress to pneumonia, hypoxia, respiratory failure, apnoea, and death. Infection rates are typically higher during the winter months, similar to other respiratory illnesses.²

Children at higher risk of developing lower respiratory tract disease include those under one year old, premature infants, and children with a history of cardiac, pulmonary, or neuromuscular diseases. At-risk groups also include individuals aged 60 years or older, those who are moderately or severely immunocompromised, and patients with COPD, congestive heart failure, haematologic disorders, chronic kidney disease, medical frailty, or residency in a long-term care facility.^2,6

Most individuals, including those hospitalised, tend to recover fully without sequelae. The majority have a good prognosis and are discharged within days. Evidence has shown no link between RSV and the development of wheezing or asthma later in life.

High-risk infants tend to have longer hospitalisations, higher rates of mechanical ventilation, and higher rates of admission to intensive care. The overall mortality rate for RSV is low, with infants with comorbidities tending to have the highest mortality.²

The diagnosis of RSV and bronchiolitis is typically clinical and does not usually require confirmatory testing or imaging. Specific testing is generally not recommended unless confirmation of diagnosis would alter medical decision-making. However, specific testing may be useful to differentiate RSV from other conditions, with rapid antigen testing and polymerase chain reaction (PCR) testing being the main options.

The sensitivity of antigen testing is approximately 80 per cent. PCR testing has a higher sensitivity rate than antigen testing but may be more expensive and require specialised equipment. X-rays may help diagnose RSV but may still make it difficult to distinguish RSV from bacterial pneumonia. Differential diagnoses include conditions such as asthma, influenza, croup, bronchitis, and pneumonia.²

Similar to other respiratory viruses, RSV should be managed by an interprofessional team that prioritises prevention. Hand-hygiene measures are among the most important methods to prevent the spread of RSV. Additionally, patients with respiratory symptoms should cover their mouth and nose with a tissue when coughing or sneezing.

Patients with RSV should avoid attending creche, school, or work, and should refrain from sharing cutlery and utensils. Cleaning contaminated surfaces, wearing appropriate personal protective equipment, and ensuring proper ventilation in rooms also help limit the spread of RSV.²

Effective passive immune prophylaxis for RSV is now available for children through monoclonal antibodies. Nirsevimab is a human recombinant monoclonal antibody with activity against RSV. It works by binding to the site at which the virus attaches to a cell, thereby preventing this binding. This process differs from vaccination, as vaccines stimulate the immune system to produce antibodies, whereas nirsevimab provides the antibodies directly to the child.

It is administered by intramuscular injection into the baby’s thigh. It provides immediate protection, with only one dose needed for the first winter season. In Ireland, all newborn babies born between September 2024 and February 2025 were offered free RSV immunisation with nirsevimab due to the high levels of RSV during the winter season. This injection may be administered in the maternity hospital or at a newborn baby health check.

Nirsevimab has demonstrated proven safety and is more than 80 per cent effective, offering protection for up to 150 days when the risk of severe infection is high. Adverse effects are typically mild and may include redness at the injection site, fever, and rash. Nirsevimab reduces the risk of contracting RSV, decreases hospitalisations, and lowers the risk of complications.^2,7

The first vaccines against RSV were approved by the European Medicines Agency in 2023. These vaccines stimulate the production of neutralising antibodies and promote the formation of memory B and T cells. The vaccines are indicated for adults aged 60 and older, with one also indicated for pregnant women at 32-36 weeks’ gestation. This is based on the premise that the transplacental transfer of maternal antibodies provides passive protection to the infant during the first few months of life.

Influenza and Tdap vaccines are both administered to pregnant women for similar purposes. Both vaccines are administered intramuscularly. These vaccines are generally well-tolerated, with pain and inflammation at the site of injection being common adverse effects. Systemic adverse effects may include fever, fatigue, myalgia, headache, fever, and malaise. Severe allergic reactions, including anaphylaxis, are rare but can potentially occur.⁶

Treatment

The mainstay of treatment for patients with RSV is supportive care. The majority of cases are self-limiting and do not require medical intervention. Ribavirin is an antiviral drug used in the treatment of RSV infection in the United States. However, it is not licensed in Ireland or recommended by European guidelines for the routine treatment of RSV. This is due to inconsistent evidence regarding its efficacy, its adverse effect profile, the cost, and its complex delivery system.

Treatment may depend on the presentation and severity of disease. Adequate hydration should be ensured, with nasal suction or lubrication as potential options to provide relief from nasal congestion. Antipyretics, including paracetamol and non-steroidal anti-inflammatory drugs, are important for reducing fever while also providing pain relief. Hospitalisation may be required if there are signs of respiratory distress.

Supplemental oxygen may be indicated for hypoxaemia, with continuous positive airflow pressure or nasal high-flow oxygen also being potential options. Patients with severe symptoms or respiratory failure may require intubation or mechanical ventilation.²