**Conflict of interest**

*The Burden of Respiratory Syncytial Virus Infection in the Young*

our hands with in ~5–10 years.

developing world.

in next few years [57].

**9. Conclusions**

• Major achievements in last 3 years are that nanoparticle based vaccines and live vector vaccines have been investigated in different phase 1 and phase 2 trials and efficient results obtained. These vaccines step forward into later phase trials for evaluation [119]. So, there is hope that safe and well tolerated vaccine candidates will provide a long lasting immunity to all target groups, may be in

• *In vitro* tissue culture system has been developed, that are being used for

• Palivizumab is only the success which is available to clinicians and is being used to reduce the burden of RSV. Palivizumab has decreased hospitalization; however, its use is limited due to high cost. There is hope that this approved prophylactic approach will be available to everyone and may soon come into extensive and widespread use. Palivizumab is patent of MedImmune and this patent is near to expire. So with expiry of this patent, there is hope that a cost effective palivizumab version will be developed. A recent technology hub has been established by the World Health Organization (WHO), the purpose of this is to increase the production of biosimilar versions [120]. There is hope that these products will be available in the market at low and affordable cost. These good initiatives will greatly reduce the mortality rates caused by RSV in

• Oral antivirals such as GS-5806 and a nucleoside analogue ALS-008176 have been passed through trials and they significantly decreased the replication of virus in human controlled experiments [121]. Nanobodies (single domain antibodies) has also been developed that protected the mice from infection and now are ready for clinical development. These results renewed the hope that an effective antiviral treatment for different risk populace will be on the horizon

One of the most common causes of the respiratory tract diseases is the RSV affecting infants, young children and the elderly people. Only supportive treatment is available such as corticosteroids, bronchodilators, oxygen supplement and ribavirin etc. which may not be occasionally effective. Palivizumab has decreased hospitalization; however, its use is limited due to high cost. Despite it is the era of progress and technology, no RSV licensed vaccine is available in the market to prevent RSV infection. Natural infection also provides partial immunity. A successful vaccine candidate will provide the long term protective immunity and must not lead to induction of enhanced RSV disease. For RSV vaccine development different target groups are being considered such as elders including pregnant women, children and infants. Each of these target groups has different challenges for vaccine development. Maternal antibodies, enhanced disease and immature immune system are the major barriers for vaccine development in the infants. The children >6 months of age have more mature immune system than infants but still can be at the risk of enhanced disease from non-live RSV vaccine. For elderly target population immune-senescence as well as pre-existing immunity is the barrier for

An ideal RSV vaccine should be safe, well tolerated and provide long lasting immunity as compared to natural infection against both RSV strains A and

predicting the efficacy and safety of candidate vaccines.

**86**

vaccine development.

There is no potential conflict of interest among the authors listed in this manuscript.
