Despite extensive research and in contrast to, for instance, MeV and MuV, no vaccines are currently available against several major pathogens of the paramyxovirus family such as RSV or different HPIVs. Infection with RSV is the leading cause of pneumonia and bronchiolitis in infants, both associated with significant mortality, while HPIV types 1 and 2 are the primary cause of croup syndrome and can likewise result in serious lower respiratory diseases such as pneumonia and bronchiolitis [4, 5] .