SARS-CoV-2 testing is dominated by PCR to guide treatment and individual as well as
public health preventive measures. Among 1700 football (soccer) players and staff of the German
Bundesliga and Bundesliga 2 who were regularly tested by PCR twice weekly, 98 individuals had a
positive PCR (May 2020 to mid-January 2021). A subset of these were retested shortly after the initial
positive result. Among those, 11 subjects were identified who only had a transient single positive PCR
of low viral load. All individuals were asymptomatic and none developed long COVID. We tested
SARS-CoV-2 IgG and IgA as well as SARS-CoV-2 specific CD4 und CD8 positive T cells, and showed
that only one out of 11 individuals developed SARS-CoV-2 specific cellular and humoral immunity
after the positive PCR, whereas a specific immunity was undetectable in all other individuals. Thus,
a single positive PCR might indicate that transient colonization of the upper respiratory tract with
SARS-CoV-2 may occur without systemic induction of specific adaptive immunity. Together with test
artifacts as another potential reason for a transiently positive test, this finding may favor cautious
interpretation of positive PCR results or retesting before initiating intervening treatment or infection
control measures in some cases
