Effectiveness of a nation-wide COVID-19 vaccination program in Mexico

BACKGROUNDVaccination has been effective in ameliorating the impact of COVID-19. However, estimation of vaccine effectiveness (VE) is still unavailable for some widely used vaccines and underrepresented groups. Here, we report on the effectiveness of a nation-wide COVID-19 vaccination program in Mexico. METHODSWe used a test-negative design within a national COVID-19 surveillance system to assess VE of the BNT162b2, mRNA-12732, Gam-COVID-Vac, Ad5-nCoV, Ad26.COV2.S, ChAdOx1 and CoronaVac vaccines, against SARS-CoV-2 infection, COVID-19 related hospitalization and death for adults [≥]18 years in Mexico. VE was estimated using Cox proportional hazard models considering time-varying vaccination status in partial and fully vaccinated individuals compared to unvaccinated adults, adjusted by age, sex, comorbidities and municipality. We also estimated VE for adults [≥]60 years, for cases with diabetes and comparing periods with predominance of variants B.1.1.519 and B.1.617.2. RESULTSWe assessed 793,487 vaccinated compared to 4,792,338 unvaccinated adults between December 24th, 2020, and September 27th, 2021. VE against SARS-CoV-2 infection was highest for fully vaccinated individuals with mRNA-12732 (91.5%, 95%CI 90.3-92.4) and Ad26.COV2.S (82.2%, 95%CI 81.4-82.9), whereas for COVID-19 related hospitalization were BNT162b2 (84.3%, 95%CI 83.6-84.9) and Gam-COVID-Vac (81.4% 95%CI 79.5-83.1) and for mortality BNT162b2 (89.8%, 95%CI 89.2-90.2) and mRNA-12732 (93.5%, 95%CI 86.0-97.0). VE for all evaluated vaccines was reduced for adults [≥]60 years, people with diabetes, and in periods of Delta variant predominance. CONCLUSIONSAll evaluated vaccines were effective against SARS-CoV-2 infection and COVID-19 related hospitalization and death. Mass vaccination campaigns with multiple vaccine products are feasible and effective to maximize vaccination coverage.

Antibody and memory B-cell immunity in a heterogeneously SARS-CoV-2 infected and vaccinated population

Global population immunity to SARS-CoV-2 is accumulating through heterogenous combinations of infection and vaccination. Vaccine distribution in low- and middle-income countries has been variable and reliant on diverse vaccine platforms. We studied B-cell immunity in Mexico, a middle-income country where five different vaccines have been deployed to populations with high SARS-CoV-2 incidence. Levels of antibodies that bound a stabilized prefusion spike trimer, neutralizing antibody titers and memory B-cell expansion correlated with each other across vaccine platforms. Nevertheless, the vaccines elicited variable levels of B-cell immunity, and the majority of recipients had undetectable neutralizing activity against the recently emergent omicron variant. SARS-CoV-2 infection, experienced prior to or after vaccination potentiated B-cell immune responses and enabled the generation of neutralizing activity against omicron and SARS-CoV for all vaccines in nearly all individuals. These findings suggest that broad population immunity to SARS-CoV-2 will eventually be achieved, but by heterogenous paths

Inexpensive workflow for simultaneous monitoring of HIV viral load and detection of SARS-CoV-2 infection

BackgroundCOVID-19 pandemic interrupted routine care for individuals living with HIV, putting them at risk of becoming virologically unsuppressed and ill. Often they are at high risk for exposure to SARS-CoV-2 infection and severe disease once infected. For this population, it is urgent to closely monitor HIV plasma viral load (VL) and screen for SARS-COV-2 infection. MethodWe have developed a non-proprietary method to isolate RNA from plasma, nasal secretions (NS), or both. HIV, SARS-CoV-2, and human RP targets in extracted RNA are then RT-qPCR to estimate the VL and classify HIV/SARS-CoV-2 status (i.e., HIV as VL failure or suppressed; SARS-CoV-2 as positive, presumptive positive, negative, or indeterminate). We evaluated this workflow on 133 clinical specimens: 40 plasma specimens (30 HIV-seropositive), 67 NS specimens (31 SARS-CoV-2-positive), and 26 pooled plasma/NS specimens (26 HIV-positive with 10 SARS-CoV-2-positive), and compared the results obtained using the in-house extraction to those using a commercial extraction kit. ResultsIn-house extraction had a detection limit of 200-copies/mL for HIV and 100-copies/mL for SARS-CoV-2. In-house and commercial methods yielded positively correlated HIV VL (R2: 0.98 for contrived samples; 0.81 for seropositive plasma). SARS-CoV-2 detection had 100% concordant classifications in contrived samples, and in clinical NS extracted by in-house method, excluding indeterminate results, was 95% concordant (25 positives, 6 presumptive positives, and 31 negatives) to those using the commercial method. Analysis of pooled plasma/NS showed R2 of 0.91 (contrived samples) and 0.71 (clinical specimens) for HIV VL correlations obtained by both extraction methods, while SARS-CoV-2 detection showed 100% concordance in contrived and clinical specimens. InterpretationOur low-cost workflow for molecular testing of HIV and SARS-CoV-2 could serve as an alternative to current standard assays for laboratories in low-resource settings.

EVALUATION OF A RAPID ANTIGEN TEST FOR SARS-COV-2 IN SYMPTOMATIC PATIENTS AND THEIR CONTACTS: A MULTICENTER STUDY

BACKGROUNDPoint-of-care rapid tests to identify SARS-CoV-2 can be of great help because, in principle, they allow decisions to be made at the site of care for treatment, or for the separation of cohorts avoiding cross-infection, especially in emergency situations. METHODSA cross sectional study in adults requesting care in Emergency Rooms (ER), or the outpatient clinics of referral hospitals for COVID-19, to define the diagnostic characteristics of a rapid antigen test for SARS-CoV-2 (the Abbott Panbio) having as a gold standard the RT-PCR for SARS-CoV-2. Health personnel in a routine situation within an active pandemic in several cities of Mexico performed the tests. RESULTSA total of 1,069 participants with a mean age of 47 years (SD 16 years), 47% with a self-reported comorbidity, and an overall prevalence of a positive RT-PCR test of 45%, were recruited from eight hospitals in Mexico. Overall sensitivity of the Panbio test was 54.4% (95%CI 51-57) with a positive likelihood ratio of 35.7, a negative likelihood ratio of 0.46 and a Receiver-Operating Characteristics curve area of 0.77. Positivity for the rapid test depended strongly on an estimate of the viral load (Cycle threshold of RT-PCR, Ct), and the days of symptoms. With a Ct[≤]25, sensitivity of the rapid test was 0.82 (95%CI, 0.76-0.87). For patients during the first week of symptoms sensitivity was 69.6% (95%CI 66-73). On the other hand, specificity of the rapid test was above 97.8% in all groups. CONCLUSIONSThe Panbio rapid antigen test for SARS-CoV-2 has a good specificity, but due to low and heterogeneous sensitivity in real life, a negative test in a person with suggestive symptoms at a time of community transmission of SARS-CoV-2 requires confirmation with RT-PCR, and after the first week of symptoms, sensitivity decreases considerably.