Due to better sanitation and hygiene, children were first exposed to poliovirus at an older age when the maternal antibodies no longer protected them.
כללי Water & the Environment
Due to better sanitation and hygiene, children were first exposed to poliovirus at an older age when the maternal antibodies no longer protected them.
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מיין לפי
* השאלה נוספה בתאריך: 09-07-2025