10/13—Effectiveness of tests to inform COVID-19 diagnosis: a rapid systematic review
38 studies on SARS-CoV-2 virus testing and 25 studies on SARS-CoV-2 antibody testing were identified. We identified high or unclear risks of bias in the majority of studies. Pooled analysis of 16 studies (3818 patients) estimated a sensitivity of 87.8% (95% CI 81.5% to 92.2%) for an initial reverse-transcriptase PCR test. For antibody tests, 10 studies reported diagnostic accuracy outcomes: sensitivity ranged from 18.4% to 96.1% and specificity 88.9% to 100% (Jarrom et al. 2020).
Accuracy of serological testing for SARS-CoV-2 antibodies: first results of a large mixed-method evaluation study
1477 individuals were included comprising 112 SARS‐CoV‐2 positives (defined as a positive real‐time PCR result; prevalence 7.6%). The ELISAs showed sensitivities of [72.9% - 89.3%]. The specificity was above 94% for all tests.
Persistence and decay of human antibody responses to the receptor binding domain of SARS-CoV-2 spike protein in COVID-19 patients
We measured plasma and/or serum antibody responses to the receptor-binding domain (RBD) of the spike (S) protein of SARS-CoV-2 in 343 North American patients infected with SARS-CoV-2 (of which 93% required hospitalization) up to 122 days after symptom onset and compared them to responses in 1548 individuals whose blood samples were obtained prior to the pandemic. Anti-RBD IgG responses decayed slowly through 90 days with only 3 seropositive individuals seroreverting within this time period. These data suggest that RBD-targeted antibodies are excellent markers of previous and recent infection, and that IgG responses persist over the first few months after infection and are highly correlated with neutralizing antibodies.
Persistence of serum and saliva antibody responses to SARS-CoV-2 spike antigens in COVID-19 patients
Here, we profiled by enzyme-linked immunosorbent assays (ELISAs) IgG, IgA and IgM responses to the SARS-CoV-2 spike protein and its receptor-binding domain (RBD) in serum and saliva of acute and convalescent patients with laboratory-diagnosed COVID-19 ranging from 3–115 days post-symptom onset (PSO), compared to negative controls. IgG antibodies remained relatively stable up to 105 days PSO in both biofluids. This study confirms that serum and saliva IgG antibodies to SARS-CoV-2 are maintained in the majority of COVID-19 patients for at least 3 months PSO. IgG responses in saliva may serve as a surrogate measure of systemic immunity to SARS-CoV-2 based on their correlation with serum IgG responses.
Immune life history, vaccination, and the dynamics of SARS-CoV-2 over the next 5 years
The future trajectory of the Covid-19 pandemic hinges on the dynamics of adaptive immunity against SARS-CoV2. We use simple epidemiological models to explore estimates for the magnitude and timing of future Covid-19 cases given different protective efficacy and duration of the adaptive immune response to SARS-CoV-2, as well as its interaction with vaccines and nonpharmaceutical interventions. We find that variations in the immune response to primary SARS-CoV-2 infections and a potential vaccine can lead to dramatically different immune landscapes and burdens of critically severe cases, ranging from sustained epidemics to near elimination.
Fig. 5 Effect of vaccine refusal on disease dynamics.
(A) Daily proportion of vaccine-adopting susceptibles who must be immunized in order to achieve ℛ0 < 1 as a function of the fraction of the population that refuses the vaccine for different values of the duration of vaccinal immunity (compare individual curves: 1/δvax = 0.25 years: solid line, 1/δvax = 0.5 years: dashed line, and 1/δvax = 1 year: dotted line) and different values of the susceptibility to secondary infection ε (compare columns: ε = 0.5: left, ε = 0.7: middle, and ε = 1: right). Top row: homogeneous transmission between vaccine adopters and refusers (c11 = c12 = c21 = c22 = 1). Middle row: increased infection rates among vaccine refusers (c11 = 1, c12 = 1.25, c21 = 1.25, and c22 = 1.5). Bottom row: decreased infection rates among vaccine refusers (c11 = 1, c12 = 0.825, c21 = 0.825, and c22 = 0.75). (B) Maximum fraction of the population that can refuse vaccination for herd immunity to still be achieved; as a function of the contact rate among vaccine refusers c22. In (A) and (B), the transmission rate is derived from the mean value of seasonal NYC-based weekly reproduction numbers (R¯¯¯0R¯0 = 1.75) (37) (fig. S2C).
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