Related Experiment Video
Updated: Dec 17, 2025
An Improved and High Throughput Respiratory Syncytial Virus RSV Micro-neutralization Assay
Published on: January 26, 2019
Number needed to immunize to prevent RSV with extended half-life monoclonal antibody
Lyn Finelli1, Yoonyoung Choi1, Edward Goldstein2
1Center for Observational and Real-World Evidence, Merck & Co., Inc., Kenilworth, NJ 07033, USA.
Insights
New extended half-life RSV monoclonal antibodies (EHL-mAbs) show significant public health benefits. Immunizing infants with these EHL-mAbs can prevent numerous respiratory syncytial virus (RSV) cases and hospitalizations.
Area of Science:
- Pediatric Infectious Diseases
- Immunology
- Public Health
Background:
- Respiratory syncytial virus (RSV) is a major cause of respiratory illness in young children, particularly those under 6 months, premature infants, and those with cardiac or pulmonary conditions.
- Current immunoprophylaxis for RSV is limited to high-risk infants, with no licensed vaccines available.
- Extended half-life RSV monoclonal antibodies (EHL-mAbs) are being developed for broader infant immunization.
Purpose of the Study:
- To model the potential public health benefits of using EHL-mAbs for RSV immunization in infants.
- To estimate the number needed to immunize (NNI) to prevent RSV-related illnesses and hospitalizations.
Main Methods:
- Combined RSV hospitalization, outpatient visit, and lower respiratory tract infection (LRI) incidence data.
- Calculated the absolute incidence rate reduction (ARR) based on varying immunization efficacies.
- Determined the NNI by calculating the reciprocal of the ARR.
Main Results:
- For a 70% efficacy EHL-mAb, 6-18 infant immunizations prevent one outpatient visit, and 13-33 prevent one LRI outpatient visit.
- Preventing one RSV hospitalization requires immunizing 37-85 infants aged 0-5 months or 107-280 infants aged 6-11 months.
Conclusions:
- RSV EHL-mAbs, even with moderate efficacy, could offer substantial public health benefits by reducing disease burden.
- These findings support the consideration of EHL-mAbs in national immunization programs for infants.
- The data provide valuable insights for public health decision-making regarding RSV prevention strategies.
Background:
Respiratory syncytial virus (RSV) is one of the most important respiratory pathogens in young children. Infants <6 months of age and infants and young children with extreme pre-term birth, and cardiac and pulmonary co-morbidities experience the highest incidence of severe RSV disease. There are no licensed vaccines; immunoprophylaxis is recommended for the highest risk children. Extended half-life RSV monoclonal antibodies (EHL-mAbs) are under development intended for immunization of all infants and high-risk children <2 years of age. We modeled the anticipated public health benefits of RSV EHL-mAb immunization using the number needed to immunize (NNI).
Methods:
We combined RSV hospitalization, outpatient and outpatient lower respiratory tract infection (LRI) incidence estimates and a range of immunization efficacies to estimate the annual NNI. We calculated the absolute incidence rate reduction (ARR) by multiplying the incidence rates by immunization efficacy. NNI was calculated as the reciprocal of the ARR.
Results:
For an RSV EHL-mAb with 70% efficacy, 6-18 infants would need to be immunized to prevent one RSV-associated outpatient visit, and 13-33 infants would need to be immunized to prevent one RSV-associated LRI outpatient visit. To prevent one RSV-associated hospitalization, 37-85 infants 0-5 months of age, and 107-280 infants 6-11 months of age would need to be immunized.
Conclusions:
Public health benefits, such as disease cases averted due to immunization, are essential elements in consideration of candidate vaccines for a national immunization program. An RSV EHL-mAb of moderate efficacy could have high impact. These data provide an additional perspective for public health decision making.
