A series of diagnostic contamination events from seasonal influenza vaccines

Polymerase chain reaction (PCR) is the preferred method for diagnosing influenza infections and enables differentiation between influenza A and B viruses, as well as influenza A subtypes and influenza B lineages. However, the high sensitivity of PCR can also render it vulnerable to false-positive results due to contamination. During the 2022–2023 influenza season in Norway, an unusual pattern of pre-epidemic diagnostic samples testing positive for both influenza A and B or for the presumably extinct B/Yamagata-lineage, raised suspicion of external contamination. A retrospective review of test data revealed an increased frequency of unusual influenza detection patterns, particularly between weeks 42 and 46 of 2022, coinciding in time with the peak of the national influenza vaccination campaign. During this period, the prevalence of suspected vaccine-contaminated samples reached 3.45% of all Influenza positive samples. Environmental sampling from vaccination locations with detection of both influenza A and B RNA further supported the suspicion of influenza vaccine derived contamination. The detection in suspect diagnostic specimens of several influenza types/subtypes/lineages in one same specimen, including detection of the presumably extinct B/Yamagata lineage, corroborated that the seasonal influenza vaccine was the likely source of contamination. These findings highlight the risk of contamination of diagnostic samples with RNA from the influenza virion-derived vaccines and that these contaminations could have implications for diagnostic accuracy and public health surveillance.

Note:
Funding Information: The research was funded by the budget of the Influenza Surveillance Program at the Norwegian Institute of Public Health, as part of the mandate of the National Influenza Center.

Declaration of Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Keywords: influenza, inactivated vaccine, diagnostic test, contamination

Suggested Citation: Suggested Citation

Rohringer, Andreas and Ebbesen, Marit H. and Fossum, Even and Nygaard, Randi M. and Madsen, Birgitte B. and Larsdatter Storm, Margrethe and Aasand, Nina and Rydland, Kjersti and Bragstad, Karoline and Hungnes, Olav, A series of diagnostic contamination events from seasonal influenza vaccines. Available at SSRN: https://ssrn.com/abstract=5611368 or http://dx.doi.org/10.2139/ssrn.5611368