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Infectious Diseases
Division Faculty
Research
Laboratory Research
Patient-Oriented Research
Creech Lab
Natasha Halasa, M.D., M.P.H.
Vanderbilt Vaccine Research Program
International Health Research
Pediatric Infectious Diseases Fellowship
Patient Care
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Antibiotic Prescribing Practices
Dr. Halasa's initial studies focused on antibiotic prescribing practices in different types of outpatient settings. She documented important trends in the types of antibiotics prescribed and discovered substantial differences in prescribing practices in community and university-based settings. She also noted differences in prescribing practices based on race. These findings resulted in first-author publications in the Pediatric Infectious Diseases Journal and the Journal of Pediatrics and formed the basis of her M.P.H. thesis research.

Pertussis Immunization of Neonates
Dr. Halasa's more recent work has focused on immunization of neonates with pertussis vaccine. Dr. Halasa became interested in this problem while caring for several infants at Children's Hospital with fatal pertussis. Her observations led to a report in Pediatrics and an editorial in Journal of Pediatrics. These experiences prompted the hypothesis that pertussis immunization in the immediate newborn period might diminish the risk of fatal pertussis in young infants. To attempt to confer earlier protection against pertussis in infants, Dr. Halasa designed the proposed study of infant immunization. 

This study investigated the administration DTaP dose at 2-14 days of life in addition to the recommended vaccine schedule, to determine safety and immunogenicity of the vaccine in this age group. This was a pilot study and enrolled a total of 50 subjects, with 25 subjects receiving a birth dose and 25 subjects receiving the recommended schedule of vaccination. These infants were followed-up until 23 months of age. Dr. Halasa and her team discovered that the birth dose group had lower titers to all four of the pertussis antigens at 7 months of age and three out of four pertussis antigens at 18 months of age compared to the control group. This study has been completed and was accepted for publication in Journal of Pediatrics. Over the past years, Dr. Halasa has presented this work in poster presentations at Pediatric Infectious Diseases meeting in Memphis, the Pediatric Academic Society in Washington, D.C., the Interscience Conference on Antimicrobial Agents and Chemotherapy in San Francisco, the Pertussis meeting in Paris, and as oral presentations at ICAAC in Washington, D.C., Pertussis meeting in Atlanta, Georgia, and Neonatal Meeting in Madrid, Spain in which she also received a young investigator award.    

Influenza Vaccine: Safety and Immunogenicity
Dr. Halasa was the primary investigator in a pilot study investigating the safety and immunogenicity of the administration of the influenza vaccine in infants 10-22 weeks of age.  During  the initial year of the study (2004-2005) 19 subjects were recruited into the study and during the second year (2005-2006) an additional Vaccine Trials Evaluation Unit (VTEU) site, the University of Cincinnati, was added and both sites recruited a total of 23 infants (13 at the Vanderbilt site and 10 at the Cincinnati site).  In this prospective pilot study, healthy subjects between the ages of 10-22 weeks received two 0.25 ml doses of the 2004-2005 or 2005-2006 TIV formulation separated by at least 28 days and from routine infant immunizations by 14 days. Dr. Halasa and her team discovered that it was safe to administer TIV to this age group, but infants who had pre-existing influenza antibody titers were less likely to have four-fold rise in antibody titers compared to infants who did not have pre-existing influenza antibody titers. This work was presented at the Infectious Diseases Society of America conference in October of 2006. This work is published in Journal of Infectious Diseases. Dr. Halasa also submitted a concept she to the VTEU to further investigate the immune responses of these young infants. 

Assessing the Rates of Invasive Pneumococcal Disease
With the licensure of pneumococcal conjugate vaccine, Dr. Halasa participated in the assessment of the rates of invasive pneumococcal disease in Tennessee as part of the CDC-funded Active Bacterial Core surveillance network.  These data have resulted in several publications which demonstrated a marked decline in invasive pneumococcal disease, including antibiotic-resistant strains, in the two years since the introduction of the 7-valent conjugate pneumococcal vaccine. Dr. Halasa was also involved in determining the impact of the conjugate vaccine on the burden of invasive pneumococcal disease in children with sickle-cell disease using the TennCare database. In collaboration with Drs. Marie Griffin and Sadhna Shankar and others, this work was published in Clinical Infectious Diseases Journal, and demonstrated over 90% reduction of invasive pneumococcal disease in children with sickle-cell disease. This abstract was also selected as the Program Committee Choice Award at the IDSA conference in 2005. 

Multi-Center Vaccine Trials
Dr. Halasa also participates in multi-center vaccines trials with respiratory viral vaccines.  For example, Dr. Halasa is involved in a trial investigating the safety and immunogenicity of the administration of the cold-adapted influenza vaccine in children who are immunosuppressed. This study enrolled 20 subjects, and her site was the second highest in recruitment. Most recently, Dr. Halasa is involved in a PIV3 and RSV vaccine trial with young infants. 

International Collaboration
In order to understand the viral burden in young children in Amman, Jordan, Dr. Halasa collaborated with Dr. Najwa Khuri-Bulos, professor and chief of Pediatric Infectious Diseases at Jordan University.  Dr. Khuri-Bulos visited Vanderbilt in October 2006 and during this visit, it was discovered that viral respiratory burden in young children was not known in this region.  So, Dr. Halasa and Dr. Khuri-Bulos together wrote the protocol, received IRB approval at both institutions, and set up a respiratory viral surveillance project in January, 2007. Dr. Halasa spent the month of January in Amman to train two study coordinators to collect data, obtain clinical specimens, and how to process the specimens for future shipment to Nashville. The data from this project were presented as poster presentation at Xth International Symposium on Respiratory Viral Infections meeting in Singapore. A major finding of this project was the extreme burden that RSV plays in hospitalized children less than five years of age, with over 60% of the 728 subjects admitted to the hospital having a positive PCR for RSV. These findings are important if and when a RSV vaccine becomes available. Dr. Halasa and Dr. Khuri-Bulos are working on securing funding to continue this project. 

Funding
Dr. Halasa has garnered substantial grant support for her training. She was initially funded by the Molecular Basis of Infectious Diseases Training Grant (NIAID) and the Vanderbilt Mentored Clinical Research Scholars (VCRS) program (institutional K12 grant). She is currently funded by an NIH individual K23 grant.  She also receives support from investigator-initiated grants from Sanofi Pasteur for her neonatal pertussis immunization studies and the evaluation of cell-mediated immunity following pertussis and influenza vaccines.

 



 
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Monroe Carrell Jr. Children's Hospital at Vanderbilt