1. Department of Biomedicine and Prevention, University of Rome Tor Vergata, Rome, Italy.
2. National Centre for Diseases Prevention and Health Promotion, National Institute of Health, Rome, Italy.
3. Italian National Committee for UNICEF, Rome, Italy.
4. Mother and Child Health Unit, ATS Città Metropolitana di Milano, Milan, Italy.
5. National Institute for Infectious Diseases ‘Lazzaro Spallanzani’, Rome, Italy.