RSV: lack of vaccine puts most
vulnerable at risk
An infection with the respiratory syncytial virus can result in
hospitalization and sometimes respiratory failure. With no suitable treatment
available and the only preventative medication considered too expensive to be
widely prescribed, the need for an effective vaccine is high. However, given
the failure of recent developmental efforts the launch of a successful vaccine
is still some time away.
An infection by the respiratory syncytial virus (RSV) usually causes upper
respiratory tract infections (URTIs), resulting in symptoms of the common
cold. However, in certain risk groups, RSV can also cause lower respiratory
tract infections (LRTIs). When RSV causes severe LRTIs, these usually manifest
as bronchiolitis or pneumonia, which can lead to respiratory failure. The most
important risk factors include prematurity, underlying cardiac or pulmonary
disease, compromised immune system and old age. Other risk factors are related
to the environment of the patient, such as crowded living conditions and
exposure to tobacco smoke.
Datamonitor estimates that a total of 18 million people annually become
infected by RSV in the seven major markets (US, Japan, France, Germany, Italy,
Spain, UK), including three million adults with underlying disease and almost
400,000 premature infants. Approximately 900,000 of the individuals in these
risk groups are hospitalized for this infection each year. Although mortality
is low, the high number of hospitalizations makes RSV a costly disease.
Treatment options limited
The RSV market is currently dominated by MedImmune's prophylaxis Synagis (palivizumab),
a recombinant human monoclonal antibody. Synagis was launched in 1998 and now
has sales of around $750 million per RSV (winter) season. Although Synagis is
quite effective in preventing RSV hospitalizations, its cripplingly high costs
mean that its use is limited to the most vulnerable risk groups: premature
infants and children with chronic lung disease or congenital heart disease.
In addition to this prophylaxis, Valeant Pharmaceuticals' Virazole is the only
treatment on the market for RSV. However, this drug has fallen out of favor
because of its limited efficacy and only reached sales of $2.5 million in the
most recent RSV season. An effective vaccine to prevent RSV in the most
vulnerable population groups is essential, rather than using drugs with little
efficacy.
Road to successful RSV vaccine full of hurdles
Despite the high need for an RSV vaccine, many large vaccine companies have
abandoned their developing efforts. The main reason is thought to be
financial, although disease specific difficulties also play a role. The two
major patient groups - elderly and infants - dwell at the opposite ends of the
age spectrum, each presenting their own problems. Furthermore, the moral and
ethical dilemma of testing new drugs on premature babies is very difficult to
resolve for both parents and clinicians. Finally, the respiratory syncytial
virus itself has several characteristics that makes the development of
vaccinations difficult.
Again, it is MedImmune that dominates the limited RSV vaccine development;
with MEDI-534 the most advanced RSV vaccine in the pipeline. Nevertheless,
this drug is currently in phase I clinical development, which means that a
vaccine for RSV is still a long way from being ready to be prescribed.
Diagnosis difficulty
The peak incidence of RSV infections occurs in the winter months, usually
coinciding with the influenza epidemic. Since symptoms of influenza and RSV
are similar, it is difficult to make a correct diagnosis without specific
tests. A rapid diagnosis of RSV in people admitted to hospital can help
prevent nosocomial transmission, since patients can be either assigned to
private rooms or cohorted with other RSV infected patients. Additionally, a
faster negative RSV diagnosis may offer the patient a chance of a more rapid
treatment of, for example, bacterial infections or influenza. Nevertheless,
since there is currently no specific treatment for RSV infections, physicians
do not always value diagnosis as important.
Viral cultures are considered the gold standard method of RSV diagnosis.
However, specific confirmation generally requires several days, presenting a
dilemma for patients who may require immediate treatment. Antigen detection
assays have become a common rapid method of detection, although all of these
tests lack sensitivity, making them only appropriate during epidemics, when
high volumes of tests need to be performed in a short time span.
While RSV is a common virus causing only cold-like symptoms in healthy
individuals, it can be very dangerous for the more vulnerable people of
society. The high costs of available prophylaxis combined with under-diagnosis
and a lack of effective treatment mean that more people suffer serious
complications from an infection with this virus than necessary. A vaccine
would mean a big step forward in the prevention of hospitalizations and maybe
even deaths, however, it will take some time before a vaccine reaches the
people who need it most.
Related research:
Stakeholder Opinions: Respiratory Syncytial Virus (RSV) - A market yet to
reach its full potential
Stakeholder Insight: Respiratory Tract Infections in the USA - The demise of
narrow-spectrum antibiotics
Commercial Insight: Herpes and Respiratory Antivirals - Leaders Rise and Fall
