RSV vaccine

A respiratory syncytial virus vaccine (RSV vaccine) is specifically formulated to protect individuals from infections instigated by the respiratory syncytial virus. Over the years, extensive research has been conducted to develop an effective vaccine against RSV, culminating in the recent approval of several vaccines for public use.

Approved RSV Vaccines

There are two FDA approved RSV vaccines available in the United States. 1. Arexvy (GSK) - Approved in the United States in May 2023.

• Received approval for medical use in the European Union in June 2023.
• Sanctioned for use in Canada for adults aged 60 and above in August 2023.

2. Abrysvo (Pfizer) - from Merck.

• Approved in the U.S. in May 2023, including for use in pregnant individuals in August 2023 to protect infants from birth through six months against severe RSV infections.
• The European Commission approved its use for infants up to six months of age as well as older adults in the European Union in August 2023.

FDA Approval of RSV Vaccine Arexvy

In May 2023, the U.S. Food and Drug Administration (FDA) approved Arexvy, marking it as the inaugural respiratory syncytial virus (RSV) vaccine to receive such approval in the United States. The vaccine is primarily aimed at individuals aged 60 and above for the prevention of lower respiratory tract disease (LRTD) attributable to RSV.

The Significance of RSV

RSV is recognized as a highly contagious pathogen responsible for instigating infections in the lungs and respiratory passages across all age groups. The transmission of this virus displays seasonality, often initiating during the autumn months and reaching its peak during winter. Among the elderly, particularly those aged 65 and older, RSV emerges as a prevalent cause behind LRTD. Such infections can escalate into grave conditions such as pneumonia and bronchiolitis – the latter being characterized by the swelling of tiny airway passages within the lungs. Data from the U.S. Centers for Disease Control and Prevention (CDC) illustrates the severity of RSV, linking it to an annual figure of 60,000-120,000 hospitalizations and a staggering 6,000-10,000 fatalities among the senior U.S. populace.

Peter Marks, M.D., Ph.D., who presides over the FDA’s Center for Biologics Evaluation and Research, emphasized the urgency and necessity of this vaccine by stating, “Older adults, especially those plagued by underlying health afflictions such as cardiovascular or pulmonary diseases or compromised immune systems, are profoundly susceptible to the severe manifestations of RSV.” He hailed the approval of Arexvy as a monumental stride in public health, underscoring the FDA’s unwavering dedication to ushering in potent and safe vaccines for American use.

Studies and Clinical Trials

The endorsement of Arexvy's safety and efficacy hinged on the FDA's rigorous scrutiny of data procured from an ongoing randomized, placebo-controlled clinical trial. This international study focused on participants aged 60 and above. The principal objective of the trial was to evaluate the repercussions of a single-dose administration in this age group. To gauge the long-term effectiveness and potential needs for repeat vaccinations, subjects will continue to be monitored for three RSV seasons.

From the preliminary RSV season, the following data was available for the FDA's perusal:

• Roughly 12,500 participants were administered Arexvy while an equivalent number received a placebo.
• Among these subjects, Arexvy showcased a pronounced reduction in the risk of contracting RSV-linked LRTD by 82.6% and curtailed the risk of its severe form by a remarkable 94.1%.

Additionally, in this clinical trial, a prevalent set of side effects emerged, which comprised:

• Injection site discomfort
• Fatigue
• Myalgia (muscle pain)
• Headaches
• Arthralgia (joint stiffness/pain)

Interestingly, atrial fibrillation within 30 days post-vaccination was reported in 10 individuals administered Arexvy, as opposed to 4 in the placebo group.

• Two separate investigations involving about 2,500 participants each, all aged 60 or older, also provided Arexvy. One particular study, which administered Arexvy simultaneously with an FDA-endorsed flu vaccine, revealed two instances of acute disseminated encephalomyelitis (ADEM) – a rare inflammatory condition impacting the brain and spinal cord. Tragically, one of these cases culminated in the patient's demise. In another study, an occurrence of Guillain-Barré syndrome was reported just nine days post-vaccination with Arexvy. This rare ailment sees the body's immune system inadvertently attacking nerve cells, leading to muscle feebleness and, in some instances, paralysis.

FDA approval of Abryvso

Abrysvo is a new vaccine developed for the prevention of lower respiratory tract disease (LRTD) and severe LRTD resulting from the respiratory syncytial virus (RSV) in neonates aged between birth and 6 months. Notably, it stands as the very first vaccine to receive FDA approval for administration in pregnant individuals.

Indications and Usage

• Abrysvo can be administered to pregnant individuals from the gestational age of 32 up to 36 weeks to prevent RSV-induced LRTD and severe LRTD in infants from birth to 6 months.
• The recommended regimen involves a solitary intramuscular injection dose.
• Previously, in May, the FDA approved Abrysvo for RSV LRTD prevention in those aged 60 years and older.

Clinical Study Outcomes

Extensive, ongoing randomized placebo-controlled international clinical studies have evaluated Abrysvo's safety and efficacy.

• In a pivotal clinical trial:
• Abrysvo was provided to approximately 3,500 pregnant individuals, while an equivalent number received a placebo.
• Abrysvo demonstrated a reduction in the risk of severe LRTD by 81.8% within 90 days post birth and by 69.4% within 180 days.
• For a subgroup in the 32-36 weeks gestational age, the risks of LRTD and severe LRTD dropped by 34.7% and 91.1%, respectively, within 90 days of birth. These figures further improved to 57.3% and 76.5% within 180 days.

Safety Assessment

The vaccine's safety was probed through two studies:

• The primary study involved approximately 3,600 participants for both the vaccine and placebo groups.
• A secondary study had about 100 pregnant participants in both cohorts.

Common side effects manifested as:

• Injection site pain
• Headaches
• Muscle aches
• Nausea

Moreover, rarer occurrences included:

• A hypertensive disorder, pre-eclampsia, in 1.8% vaccine recipients compared to 1.4% in the placebo group.
• Infants born to vaccinated mothers exhibited higher incidences of low birth weight and jaundice compared to those born to placebo recipients.

Prescribing Information Warning

Abrysvo's prescribing information encompasses a warning pertaining to a 5.7% rate of preterm births in vaccine recipients, contrasted with 4.7% in placebo recipients. Data remains inconclusive about a causal link between Abrysvo and preterm births. Accordingly:

• Healthcare providers are advised to administer Abrysvo between 32 and 36 weeks of gestation to mitigate potential risks of preterm births.
• Pregnant individuals at an elevated risk of preterm birth were predominantly excluded from Abrysvo clinical trials.

Postmarketing Studies

The FDA has mandated postmarketing studies from the producing company to:

• Explore the potential risk link between preterm birth and Abrysvo.
• Assess hypertensive pregnancy disorders, including pre-eclampsia.

References

• U.S. Food and Drug Administration. "FDA Approves Arexvy – The First RSV Vaccine." May 2023.
• U.S. Centers for Disease Control and Prevention. "RSV in the United States: Statistics and Surveillance." 2022.
• Marks, Peter, M.D., Ph.D. "Statement on the Approval of Arexvy." FDA’s Center for Biologics Evaluation and Research, May 2023.

Also see

• Respiratory syncytial virus

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