 በ7,000 ግዛቶች ውስጥ በኮቪድ መሰል ህመም የተያዙ ከ9 በላይ ሰዎችን በመረመረው አዲስ MMWR፣ ሲዲሲ ያልተከተቡ እና በቅርብ ጊዜ በቫይረሱ   የተያዙ ሰዎች በቅርብ ጊዜ ሙሉ በሙሉ ከተከተቡት በ 5 እጥፍ የበለጠ በኮቪድ-19 የመያዝ እድላቸው ከፍተኛ መሆኑን አረጋግጧል።
In a study of more than 7,000 people across 9 states, researchers found that those who were unvaccinated and had a recent infection were 5 times more likely to have COVID-19 than those who were recently fully vaccinated and did not have a prior infection.