Or 'internal vaccination'.

It looks like 'П\е' is ''перентерально' as here:
https://vseosvita.ua/library/embed/000kwq-5266.docx.html
...Перентарально можна ввести ліки шляхом ін'єкцій

https://pubmed.ncbi.nlm.nih.gov/335740/
... The authors evaluated the immunological results of enteral and subcutaneous injection of detergent Sonne dysentery vaccine to volunteers (changes in
https://www.jstor.org/stable/30102152
...antibody titer after enteral vaccination is an indication that the vaccine

In the vaccination chart, it is written usually about poliomyelitis vaccination
In the USA polio vaccine is in the form of injection, in Europe - the peroral vaccine is used