ABSTRACT
BackgroundThe administration of a third (booster) dose of COVID-19 vaccines in Peru initially employed the BNT162b2 (Pfizer) mRNA vaccine. The national vaccination program started with healthcare workers (HCW) who received BBIBP-CorV (Sinopharm) vaccine as primary regimen and elderly people previously immunized with BNT162b2. This study evaluated the reactogenicity and immunogenicity of the "booster" dose in these two groups in Lima, Peru. MethodsWe conducted a prospective cohort study, recruiting participants from November to December of 2021 in Lima, Peru. We evaluated immunogenicity and reactogenicity in HCW and elderly patients previously vaccinated with either two doses of BBIBP-CorV (heterologous regimen) or BTN162b2 (homologous regimen). Immunogenicity was measured by anti-SARS-CoV-2 IgG antibody levels immediately before boosting dose and 14 days later. IgG geometric means (GM) and medians were obtained, and modeled using ANCOVA and quantile regressions. ResultsThe GM of IgG levels increased significantly after boosting: from 28.5{+/-}5.0 AU/mL up to 486.6{+/-}1.2 AU/mL (p<0.001) which corresponds to a 17-fold increase. The heterologous vaccine regimen produced higher GM of post-booster anti-SARS-CoV-2 IgG levels, eliciting a 13% fold increase in the geometric mean ratio (95%CI: 1.02-1.27) and a median difference of 92.3 AU/ml (95%CI: 24.9-159.7). Both were safe and well tolerated. Previous COVID-19 infection was also associated with higher pre and post-booster IgG GM levels. ConclusionAlthough both boosting regimens were highly immunogenic, two doses of BBIBP-CorV boosted with BTN162b2 produced a stronger IgG antibody response than the homologous BNT162b2 regimen in the Peruvian population. Additionally, both regimens were mildly reactogenic and well-tolerated.
ABSTRACT
Molecular diagnosis of SARS-CoV-2 in developing countries is still a big challenge. The reference standard, RT-qPCR, recommended by WHO, is not widely available, difficulting early identification of cases. Furthermore, the transport logistic between the sample collection point and the laboratory facilities can alter the samples, producing false negative results. RT-LAMP is a cheaper, simpler molecular technique that can be an interesting alternative to be offered in hospital laboratories. We present the evaluation of a RT-LAMP for diagnosis of SARS-CoV-2 in two steps: the laboratory standardization and the clinical validation, comparing it with the standard RT-qPCR. In the standardization phase, limit of detection and robustness values were obtained using RNA from a Peruvian SARS-CoV-2 strain. It presented 100% agreement between triplicates (RT-LAMP agreement with all RT-qPCR reactions that presented Ct [≤] 30) and robustness (RT-LAMP successful reactions with 80% reaction volume and 50% primer concentration). 384 nasal and pharyngeal swabs collected from symptomatic patients and stored in the INS biobank were tested and we obtained 98.75%, 87.41%, 97.65% and 92.96% for specificity, sensitivity, positive predictive value and negative predictive values respectively. Then, 383 samples from symptomatic patients with less than 15 days of disease, were tested both with the RT-LAMP and with the RT-qPCR, obtaining e 98.8%, 88.1%, 97.7% y 93.3% of specificity, sensitivity, positive predictive value and negative predictive values respectively. The laboratory standardization and the clinical validation presented the same value by Kappa-Cohen index (0.88) indicating an almost perfect agreement between RT-LAMP and RT-qPCR for molecular detection of SARS-CoV-2. We conclude that this RT-LAMP protocol presented high diagnostic performance values and can be an effective alternative for COVID-19 molecular diagnosis in hospitals, contributing to early diagnosis and reducing the spread of virus transmission in the Peruvian population.
