Hello. Thank you for posting.
The virus can remain in the body for weeks even after the patient has recovered completely. Infection results in immunity to the specific virus that caused HFMD.
Most children (and adults) will not get hand, foot, and mouth disease again, however, there can be very rare cases when those skin lesions will surface again (milder the second time). This can be due to another, similar viral species that causes identical skin lesions, or a rare reactivation of the prior infection.