ABSTRACT
Background. To describe post-COVID-19 vaccination [fully vaccinated (FV) and first booster] immune response and occurrence of reinfection ( >90 days from prior infection) in nursing home residents (NHr) with/without evidence of prior SARS-CoV-2 infection. Methods. In a longitudinal prospective cohort of 36 NHr from 3 NHs, interviews, chart ions, and specimens [blood and anterior nasal swabs (ANs)] were collected at baseline and monthly visits. ANs underwent molecular and BinaxNOWTM antigen testing. Quantitative Meso Scale Discovery platform tested blood specimens for anti-spike (S) protein and anti-nucleocapsid (N) antibodies. In addition, in a subset (n=13), S-specific memory B cells (MBCs) were tested with ELISpot assays. Results. The cohort's median age was 72 years;46% male, 64% White Non-Hispanic, 80% had >=3 comorbidities, and 29 (81%) had prior SARS-CoV-2 infection. Of 36, 76% received Pfizer-BioNTech and 24% Moderna homologous vaccine. The median distribution of anti-S IgG concentrations among those with prior infection increased 15-30 days post-FV, remained stable for 90 days, and declined by 120 days. The anti-S IgG remained above the estimated vaccine effectiveness (VE) thresholds published [Pfizer-BioNTech (95% VE: 530 BAU/ml), Moderna (90% VE: 298 BAU/ml)]. Among those without previous infection, anti-S IgG declined after 60 days and stayed near the VE thresholds until a recent infection/booster. Age, sex, and comorbidities had no appreciable impact on anti-S IgG. From enrollment to November 2021, 1of 29 had reinfection. From December 2021 to January 2022, 2 of 7 had a new infection, and 4 of 29 had reinfection, as shown by anti-N IgG rise. Persistently low numbers of total and anti-S MBC were seen across the evaluation, even with post-booster anti-S MBC rise. There was an immediate rise in anti-S IgG concentrations in all participants post-booster, irrespective of recent infection. Conclusion. These findings from a NH convenience cohort suggest that prior SARS-CoV-2 infection has a pronounced immunomodulatory enhancing effect on the magnitude and duration of FV immune response. The decline of anti-S antibodies post-FV and rise after booster supported the booster recommendation in this cohort. The low MBC counts indicate immunosenescence in this high-risk population.
ABSTRACT
Background: Middle East respiratory syndrome coronavirus (MERS-CoV) is an emerging coronavirus that is endemic in dromedary camels. Kenya's >3 million camels have high seroprevalence of antibodies against MERS-CoV, with scant evidence of human infection, possibly due to a lower zoonotic potential of Clade C viruses, predominantly found in African camels. Methods: Between April 2018-March 2020, we followed camels aged 0-24 months from 33 camel-keeping homesteads within 50Km of Marsabit town through collecting deep nasal swabs and documenting signs of illness in camels every two weeks. Swabs were screened for MERS-CoV by reverse transcriptase (RT)-polymerase chain reaction (PCR) testing and virus isolation performed on PCR positive samples with cycle threshold (CT) <20. Both the isolates and swab samples (CT <30) were subjected to whole genome sequencing. Human camel handlers were also swabbed and screened for symptoms monthly and samples tested for MERS-CoV by RT-PCR. Results: Among 243 calves, 68 illnesses were recorded in 58 camels (53.9%);50/68 (73.5%) of illnesses were recorded in 2019, and 39 (57.3%) were respiratory symptoms (nasal discharge, hyperlacrimation and coughing). A total of 124/4,702 camel swabs (2.6%) from 83 (34.2%) calves in 15 (45.5%) enrolled compounds were positive for MERS-CoV RNA. Cases were detected between May-September 2019 with three infection peaks, a similar period when three (1.1%) human PCR-positive but asymptomatic cases were detected among 262 persons handling these herds. Sequencing of camel specimens revealed a Clade C2 virus with identical 12 nucleotide deletion at the 3' end of OFR3 region and one nucleotide insertion at the 5' region but lacked the signature ORF4b deletions of other Clade C viruses. Interpretation: We found high levels of transmission of distinct Clade C MERS-CoV among camels in Northern Kenya, with likely spillover infection to humans. These findings update our understanding of MERS-CoV epidemiology in this region.
ABSTRACT
Background. In December 2020, B.1.1.7 lineage of SARS-CoV-2 was first detected in the United States and has since become the dominant lineage. Previous investigations involving B.1.1.7 suggested higher rates of transmission relative to non-B.1.1.7 lineages. We conducted a household transmission investigation to determine the secondary infection rates (SIR) of B.1.1.7 and non-B.1.1.7 SARS-CoV-2 lineages. Methods. From January-April 2021, we enrolled members of households in San Diego County, CA, and Denver, CO metropolitan area (Tri-County), with a confirmed SARS-CoV-2 infection in a household member with illness onset date in the previous 10 days. CDC investigators visited households at enrollment and 14 days later at closeout to obtain demographic and clinical data and nasopharyngeal (NP) samples on all consenting household members. Interim visits, with collection of NP swabs, occurred if a participant became symptomatic during follow-up. NP samples were tested for SARS-CoV-2 using TaqPath™ RT-PCR test, where failure to amplify the spike protein results in S-Gene target failure (SGTF) may indicate B.1.1.7 lineage. Demographic characteristics and SIR were compared among SGTF and non-SGTF households using two-sided p-values with chi-square tests;95% confidence intervals (CI) were calculated with Wilson score intervals. Results. 552 persons from 151 households were enrolled. 91 (60%) households were classified as SGTF, 57 (38%) non-SGTF, and 3 (2%) indeterminant. SGTF and non-SGTF households had similar sex distribution (49% female and 52% female, respectively;P=0.54) and age (median 30 years, interquartile range (IQR 14-47) and 31 years (IQR 15-45), respectively). Hispanic people accounted for 24% and 32% of enrolled members of SGTF and non-SGTF households, respectively (p=0.04). At least one secondary case occurred in 61% of SGTF and 58% of non-SGTF households (P=0.66). SIR was 52% (95%[CI] 46%-59%) for SGTF and 45% (95% CI 37%-53%) for non-SGTF households (P=0.18). Conclusion. SIRs were high in both SGTF and non-SGTF households;our findings did not support an increase in SIR for SGTF relative to non-SGTF households in this setting. Sequence confirmed SARS-CoV-2 samples will provide further information on lineage specific SIRs.
ABSTRACT
Background. Background. Understanding the viral load and potential infectivity of individuals in nursing homes (NH) with repeat positive SARS-CoV-2 tests ≥ 90 days after initial infection has important implications for safety related to transmission in this high-risk setting. Methods. Methods. We collected epidemiologic data by reviewing records of a convenience sample of NH residents and staff with respiratory specimens who had positive SARS-CoV-2 rRT-PCR test results from July 2020 through March 2021 and had a SARS-CoV-2 infection diagnosed ≥ 90 days prior. No fully vaccinated individuals were included. Each contributed one repeat positive specimen ≥ 90 days after initial, which was sent to CDC and retested using rRT-PCR. Specimens were assessed for replication-competent virus in cell culture if Cycle threshold (Ct) < 34 and sequenced if Ct < 30. Using Ct values as a proxy for viral RNA load, specimens were categorized as high (Ct < 30) or low (if Ct ≥ 30 or rRT-PCR negative at retesting). Continuous variables were compared using Wilcoxon signed-rank tests. Proportions were compared using Chi-squared or Fisher's exact tests. Results. Results. Of 64 unvaccinated individuals with specimens from 61 unique NHs, 14 (22%) were sent for culture and sequencing. Ten of 64 (16%) had a high viral RNA load, of which four (6%) were culture positive and none were known variants of interest or concern (Figure 1). Median days to repeat positive test result were 122 (Interquartile range (IQR): 103-229) and 201 (IQR: 139-254), respectively, for high versus low viral load specimens (p=0.13). More individuals with high viral loads (5/10, 50%) reported COVID-19 symptoms than with a low viral load (1/27, 4%, p=0.003). Most individuals (46/58, 79%) were tested following known or suspected exposures, with no significant differences between high and low viral load (p=0.18). Conclusion. In this study, nearly 1 in 6 NH residents and staff with repeat positive tests after 90 days demonstrated high viral RNA loads and viable virus, indicating possible infectivity. While individuals with high RNA viral load may be more likely to be symptomatic, distinguishing asymptomatic individuals who have high viral loads may be difficult with timing since initial infection, other test results, or exposure history alone.
ABSTRACT
The objective of the article was to evaluate the stability of SARS-CoV-2 and SARS-CoV-1 in aerosols and on various surfaces and estimated their decay rates using a Bayesian regression model. Results showed that the stability of SARS-CoV-2 was similar to that of SARS-CoV-1 under the experimental circumstances tested. This indicates that differences in the epidemiologic characteristics of these viruses probably arise from other factors, including high viral loads in the upper respiratory tract and the potential for persons infected with SARS-CoV-2 to shed and transmit the virus while asymptomatic. The results indicate that aerosol and fomite transmission of SARS-CoV-2 is plausible, since the virus can remain viable and infectious in aerosols for hours and on surfaces up to days (depending on the inoculum shed). These findings echo those with SARS-CoV-1, in which these forms of transmission were associated with nosocomial spread and super-spreading events, and they provide information for pandemic mitigation efforts.