Received: 15 July 2020
Accepted: 1 October 2020
First Online: 7 October 2020
Ethics and consent to participate
: The study protocol was approved by the Research Ethics Committee of the Medical Research Institute, Alexandria University, Egypt. Permission was obtained from the Health and Education offices in Hodeidah governorate. Informed consent or assent to voluntarily participate was obtained from schoolchildren or their parents/guardians after explaining the study purpose.
: Not applicable.
: The authors declare that they have no competing interests.