Pre-infection antibody levels of vaccinated healthcare workers with SARS-CoV-2 breakthrough infection: A nested case-control study.

AIM: To evaluate anti-RBD IgG antibody levels and neutralizing antibody titers between the health care workers (HCWs) with breakthrough SARS-CoV-2 infection and controls. METHODS: In this nested case-case control study, we followed 548 vaccinated HCWs with homologous (only with inactivated vaccine) or heterologous (both with inactivated and BNT162b2 vaccine) vaccination for 11 months, prospectively. We obtained blood samples from the participants for quantitative anti-RBD IgG and surrogate neutralization test. The participants with SARS-CoV-2 PCR positivity (at least 14 days after the last vaccination) were considered breakthrough infection. We chose 1:2 matched controls from the cohort, according to age, sex and vaccination status. We used R version 4.0.2 for the statistical analysis. RESULTS: Sixty-five cases and 130 controls were included in the study. The number of the breakthrough infections in HCWs were correlated with the pandemic waves in Türkiye and peaked during Omicron outbreak. The median age of the cases was 39 and 78.5% were female. The cases had more comorbidities than controls, significantly (p = 0.021). All cases experienced no or mild symptoms and recovered completely. Both pre-infection anti-RBD antibody and neutralizing antibody titers did not differ between cases and matched controls (p = 0.767, p = 0.628). CONCLUSION: In this study, we showed that there was no comparable difference in humoral response after homologous or heterologous vaccination between the cases of breakthrough infection and matched controls. Compliance with infection control measures should be ensured, in combination with vaccination.

The presence of symptoms within 6 months after COVID-19: a single-center longitudinal study.

BACKGROUND: Characterizing the post-COVID health conditions is helpful to direct patients to appropriate healthcare. AIMS: To describe the presence of symptoms in COVID-19 patients within 6 months after diagnosis and to investigate the associated factors in terms of reporting symptoms. METHODS: Data of DEU-COVIMER (a telephone interview-based COVID-19 follow-up center established in a tertiary care hospital) was analyzed for SARS-CoV-2 RNA positive participants aged ≥ 18 years from November 1st, 2020, to May 31st, 2021. Symptom frequencies were stratified by demographic and clinical characteristics at one, three, and 6 months after diagnosis. With the patients who had symptoms at baseline, generalized estimating equations were applied to identify the factors associated with reporting of symptoms. RESULTS: A total of 5610 patients agreed to participate in the study. Symptom frequency was 37.2%, 21.8%, and 18.2% for the first, third, and sixth months. Tiredness/fatigue, muscle or body aches, and dyspnea/difficulty breathing were the most common symptoms in all time frames. In multivariate analysis, older age, female gender (odds ratio OR 1.74, 95% confidence interval 1.57-1.93), bad economic status (OR 1.37, 1.14-1.65), current smoking (OR 1.15, 1.02-1.29), being fully vaccinated before COVID-19 (OR 0.53, 0.40-0.72), having more health conditions (≥ 3 conditions, OR 1.78, 1.33-2.37), having more symptoms (> 5 symptoms, OR 2.47, 2.19-2.78), and hospitalization (intensive care unit, OR 2.18, 1.51-3.14) were associated with reporting of symptoms. CONCLUSIONS: This study identifies risk factors for patients who experience post-COVID-19 symptoms. Healthcare providers should appropriately allocate resources prioritizing the patients who would benefit from post-COVID rehabilitation.

An analysis of antibody response following the second dose of CoronaVac and humoral response after booster dose with BNT162b2 or CoronaVac among healthcare workers in Turkey.

Limited data are available on the short- to midterm levels of antibodies to the CoronaVac vaccine and quantitative change in humoral response after homologous or heterologous booster doses. In this prospective cohort study, we evaluated the anti-receptor-binding domain (RBD) immunoglobulin G (IgG) levels after two doses of CoronaVac and heterologous/homologous booster administration among healthcare workers in a university hospital in Turkey. Quantitative anti-RBD IgG antibody levels were measured at first and fourth months in 560 healthcare workers who had completed two doses of CoronaVac vaccine, and within 2 months after the third dose of CoronaVac or BNT162b2. Participants were asked to complete a questionnaire during the first blood draw. The seropositivity rate was 98.9% and 89.1%, and the median antibody level was 469.2 AU/ml and 166.5 AU/ml at first and fourth month, respectively. In the fourth month, a mean reduction of 61.4% ± 20% in antibody levels was observed in 79.8% of the participants. The presence of chronic disease (odds ratio [OR]: 1.76, 95% confidence interval [CI]: 1.15-2.69) and being in the 36-50 age group (OR: 2.11, 95% CI: 1.39-3.19) were identified as independent predictors for low antibody response. The antibody level increased 104.8-fold (median: 17 609.4 vs. 168 AU/ml) and 8.7-fold (median: 1237.9 vs. 141.4 AU/ml) in the participants who received BNT162b2 and CoronaVac, respectively. During the follow-up, 25 healthcare workers (4.5%) were infected with severe acute respiratory syndrome coronavirus 2. Considering the waning immunity and circulating variants, a single booster dose of messenger RNA vaccine seems reasonable after the inactivated vaccine especially in risk groups.

Transmission dynamics and timing of key events for SARS-CoV-2 infection in healthcare workers.

BACKGROUND: Healthcare workers (HCWs) have increased risk for SARS-CoV-2 infection via contacts in hospitals, as well as via transmission in the community. Serial interval, which is defined as the time between symptom onsets in an infector-infectee pair, and the incubation period are key parameters in determining the control strategies for COVID-19. This study aimed to evaluate surveillance of HCWs and estimate the serial interval and incubation period of COVID-19. METHODS: A total of 149 HCWs and 36 certain infector-infectee pairs between 19th March 2020 and 1st November 2020 in a university hospital were included in the study. Epidemiological characteristics were recorded. Serial interval and incubation period were estimated using parametric accelerated failure time models. RESULTS: Forty HCWs (26.8%) were detected via contact-based surveillance. Of 100 HCWs epidemiologically linked with a confirmed COVID-19 case, 36 (36%) had contact with a colleague. The median serial interval was 3.93 days (95% CI: 3.17-4.83). Of symptomatic HCWs, 97.5% had developed symptoms 13.71 (95% CI: 9.39-18.73) days after symptom onset of the primary case. The median incubation period was 3.99 (95% CI: 3.25-4.84) days. Of symptomatic HCWs, 97.5% developed symptoms within 9.49 (95% CI: 6.75-12.20) days after infection. CONCLUSIONS: The serial interval and the incubation period of COVID-19 in HCWs were shorter than in the general population. Rigorous contact tracing and isolation of infected HCWs could have resulted in shorter serial intervals. Implementation of more stringent in-hospital control measures focussed on transmission between HCWs should be considered.