Assessment of Anti-SARS-CoV-2 antibody levels among university students vaccinated with different COVID-19 primary and booster doses - fall 2021, Wisconsin.

BACKGROUND: University students commonly received COVID-19 vaccinations before returning to U.S. campuses in the Fall of 2021. Given likely immunologic variation among students based on differences in type of primary series and/or booster dose vaccine received, we conducted serologic investigations in September and December 2021 on a large university campus in Wisconsin to assess anti-SARS-CoV-2 antibody levels. METHODS: We collected blood samples, demographic information, and COVID-19 illness and vaccination history from a convenience sample of students. Sera were analyzed for both anti-spike (anti-S) and anti-nucleocapsid (anti-N) antibody levels using World Health Organization standardized binding antibody units per milliliter (BAU/mL). Levels were compared across categorical primary COVID-19 vaccine series received and binary COVID-19 mRNA booster status. The association between anti-S levels and time since most recent vaccination dose was estimated by mixed-effects linear regression. RESULTS: In total, 356 students participated, of whom 219 (61.5%) had received a primary vaccine series of Pfizer-BioNTech or Moderna mRNA vaccines and 85 (23.9%) had received vaccines from Sinovac or Sinopharm. Median anti-S levels were significantly higher for mRNA primary vaccine series recipients (2.90 and 2.86 log [BAU/mL], respectively), compared with those who received Sinopharm or Sinovac vaccines (1.63 and 1.95 log [BAU/mL], respectively). Sinopharm and Sinovac vaccine recipients were associated with a significantly faster anti-S decline over time, compared with mRNA vaccine recipients (P <.001). By December, 48/172 (27.9%) participants reported receiving an mRNA COVID-19 vaccine booster, which reduced the anti-S antibody discrepancies between primary series vaccine types. CONCLUSIONS: Our work supports the benefit of heterologous boosting against COVID-19. COVID-19 mRNA vaccine booster doses were associated with increases in anti-SARS-CoV-2 antibody levels; following an mRNA booster dose, students with both mRNA and non-mRNA primary series receipt were associated with comparable levels of anti-S IgG.

Multicenter feasibility study to assess external quality assessment panels for Xpert MTB/RIF assay in South Africa.

External quality assessment (EQA) for the Xpert MTB/RIF assay is part of the quality system required for clinical and laboratory practice. Five newly developed EQA panels that use different matrices, including a lyophilized sample (Vircell, Granada, Spain), a dried tube specimen (CDC), liquid (Maine Molecular Quality Control, Inc. [MMQCI], Scarborough, ME), artificial sputum (Global Laboratory Initiative [GLI]), and a dried culture spot (National Health Laboratory Services [NHLS]), were evaluated at 11 GeneXpert testing sites in South Africa. The panels comprised Mycobacterium tuberculosis complex (MTBC)-negative, MTBC-positive (including rifampin [RIF] susceptible and RIF resistant), and nontuberculosis mycobacterial material that was inactivated and safe for transportation. Twelve qualitative and quantitative variables were scored as acceptable (1) or unacceptable (0); the overall panel performance score for the Vircell, CDC, GLI, and NHLS panels was 9 of 12, while the MMQCI panel scored 6 of 12 (owing to the need for cold chain maintenance). All panels showed good compatibility with Xpert MTB/RIF testing, and none showed PCR inhibition. The use of a liquid or dry matrix did not appear to be a distinguishing criterion, as both matrices had reduced scores on insufficient volumes, a need for extra consumables, and the ability to transfer to the Xpert MTB/RIF cartridge. EQA is an important component of the quality system required for diagnostic testing programs, but it must be complemented by routine monitoring of performance indicators and instrument verification. This study aims to introduce EQA concepts for Xpert MTB/RIF testing and evaluates five potential EQA panels.