Timing of last COVID-19 vaccine dose and SARS-CoV-2 breakthrough infections in fully (boosted) vaccinated healthcare personnel.

AIM: To estimate the incidence, timing, and severity of SARS-CoV-2 breakthrough infections in fully vaccinated healthcare personnel (HCP). METHODS: We prospectively studied 6496 fully vaccinated HCP from November 15, 2021 through April 17, 2022. Full COVID-19 vaccination was defined as a complete primary vaccination series followed by a booster dose at least six months later. RESULTS: A total of 1845 SARS-CoV-2 breakthrough infections occurred (28.4 episodes per 100 HCP), of which 1493 (80.9%) were COVID-19 cases and 352 (19.1%) were asymptomatic infections. Of the 1493 HCP with COVID-19, 4 were hospitalized for 3-6 days (hospitalization rate among HCP with COVID-19: 0.3%). No intubation or death occurred. SARS-CoV-2 breakthrough infections occurred at a mean of 16.2 weeks after the last vaccine dose. Multivariable regression analyses showed that among the 1845 HCP with a breakthrough infection, the administration of a COVID-19 vaccine dose >16.2 weeks before the infection was associated with an increased likelihood in developing COVID-19 rather than asymptomatic SARS-CoV-2 infection (OR: 1.58; 95% CI: 1.01-2.46; p-value=0.045) compared to administering a vaccine dose later. The likelihood of developing COVID-19 versus asymptomatic infection increased by 7% weekly after the last COVID-19 vaccine dose (OR: 1.07; 95% CI: 1.03-1.11; p-value=0.001). CONCLUSION: SARS-CoV-2 breakthrough infections are common among fully (boosted) vaccinated HCP. However, full COVID-19 vaccination offered considerable protection against hospitalization. Our findings may contribute to defining the optimal timing for booster vaccinations. More efficient COVID-19 vaccines that will also confer protection against SARS-CoV-2 infection are urgently needed.

Association between COVID-19 vaccination status, time elapsed since the last vaccine dose, morbidity, and absenteeism among healthcare personnel: A prospective, multicenter study.

AIM: We assessed the impact of COVID-19 vaccination status and time elapsed since the last vaccine dose on morbidity and absenteeism among healthcare personnel (HCP) in the context of a mandatory vaccination policy. METHODS: We followed 7592 HCP from November 15, 2021 through April 17, 2022. Full COVID-19 vaccination was defined as a primary vaccination series plus a booster dose at least six months later. RESULTS: There were 6496 (85.6 %) fully vaccinated, 953 (12.5 %) not fully vaccinated, and 143 (1.9 %) unvaccinated HCP. A total of 2182 absenteeism episodes occurred. Of 2088 absenteeism episodes among vaccinated HCP with known vaccination status, 1971 (94.4 %) concerned fully vaccinated and 117 (5.6 %) not fully vaccinated. Fully vaccinated HCP had 1.6 fewer days of absence compared to those not fully vaccinated (8.1 versus 9.7; p-value < 0.001). Multivariable regression analyses showed that full vaccination was associated with shorter absenteeism compared to not full vaccination (OR: 0.56; 95 % CI: 0.36-0.87; p-value = 0.01). Compared to a history of ≤ 17.1 weeks since the last dose, a history of > 17.1 weeks since the last dose was associated with longer absenteeism (OR: 1.22, 95 % CI:1.02-1.46; p-value = 0.026) and increased risk for febrile episode (OR: 1.33; 95 % CI: 1.09-1.63; p-value = 0.004), influenza-like illness (OR: 1.53, 95 % CI: 1.02-2.30; p-value = 0.038), and COVID-19 (OR: 1.72; 95 % CI: 1.24-2.39; p-value = 0.001). CONCLUSIONS: The COVID-19 pandemic continues to impose a considerable impact on HCP. The administration of a vaccine dose in less than four months before significantly protected against COVID-19 and absenteeism duration, irrespective of COVID-19 vaccination status. Defining the optimal timing of boosters is imperative.

Vaccination coverage rates and attitudes towards mandatory vaccinations among healthcare personnel in tertiary-care hospitals in Greece.

OBJECTIVES: Our aim was to estimate vaccination and susceptibility rates against vaccine-preventable diseases among healthcare personnel (HCP) in eight hospitals. METHODS: Cross-sectional survey. RESULTS: A total of 1284 HCP participated (physicians: 31.3%, nursing personnel: 36.6%, paramedical personnel: 11.1%, administrative personnel: 13.2%, supportive personnel: 7.3%). Vaccination rates were 32.9% against measles and mumps, 38.1% against rubella, 5.7% against varicella, 9.2% against hepatitis A, 65.8% against hepatitis B, 31.8% against tetanus-diphtheria, 7.1% against pertussis, 60.2% against influenza, and 80.1% against COVID-19. Susceptibility rates were as follows: 27.8% for measles, 39.6% for mumps, 33.4% for rubella, 22.2% for varicella, 86.3% for hepatitis A, 34.2% for hepatitis B, 68.2% for tetanus-diphtheria, and 92.9% for pertussis. Older HCP had higher susceptibility rates against mumps, rubella, varicella, hepatitis A, hepatitis B, tetanus-diphtheria, and pertussis (p-values <0.001 for all). Mandatory vaccinations were supported by 81.85% of HCP. CONCLUSIONS: Although most HCPs supported mandatory vaccinations, significant vaccination gaps, and susceptibility rates were recorded. The proportion of susceptible HCP to measles, mumps, rubella, and varicella has increased in the past decade, mostly because of reduction in acquired cases of natural illness. Vaccination programs for HCP should be developed. A national registry to follow HCP's vaccination rates is urgently needed.

A study of the evolution of the third COVID-19 pandemic wave in the Athens metropolitan area, Greece, through two cross-sectional seroepidemiological surveys: March, June 2021.

We studied the third coronavirus disease 2019 (COVID-19) pandemic wave in Athens metropolitan area (3 738 901 inhabitants) through two seroepidemiological surveys. Persons presenting in 12 healthcare facilities across Athens in March and June 2021 were studied (764 and 901, respectively). Immunoglobulin G antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein were measured by a chemiluminescent microparticle immunoassay. In March the seroprevalence rate was 11.6%, meaning that 435 208 residents of Athens had evidence of immunity. The respective values in June were 55.7% and 2 082 568 residents. The highest seroprevalence rates attributed to SARS-CoV-2 infection were recorded in persons <18 years (16.3% in March and 31.6% in June), while immunity was mainly vaccine-induced in persons 18-64 years and >65 years. Infection-attributed immunity also increased in older-age groups. Wide ranges in seroprevalence rates were noted across areas in March and June. The highest seroprevalence rates were recorded in Piraeus (47.2%) and West Attica (37.5%). However, the highest increase (>5 times) occurred in Piraeus and the South Section of Athens, which are among the most densely populated areas in Athens. In both study periods, history of COVID-19 or febrile episode, and having a cohabitant with COVID-19 were associated with increased risk for seropositivity among unvaccinated persons (p values <0.001 for all). Residing in Piraeus, the South Section or West Attica was associated with increased risk for seropositivity in June (p values <0.001). Wide heterogeneity in seroprevalence rates was found across areas in Athens, which is mainly attributed to population density. The impact of population mobility and socioeconomic status should be explored.

COVID-19 vaccination significantly reduces morbidity and absenteeism among healthcare personnel: A prospective multicenter study.

AIM: Healthcare personnel (HCP) are prioritized for coronavirus disease 2019 (COVID-19) vaccination to protect them and non-disruptive provision of healthcare services. We assessed the impact of the Pfizer-BioNTech vaccine on morbidity and absenteeism among HCP. METHODS: We studied 7445 HCP in five tertiary-care hospitals in Greece from November 15, 2020 through April 18, 2021. RESULTS: A total of 910 episodes of absenteeism and 9695 days of absence were recorded during the entire study period. Starting from January 4, 2021, 4823/7445 HCP (64.8%) were fully or partially vaccinated. Overall, 535 episodes of absenteeism occurred from January 4, 2021 through April 18, 2021, including 309 (57.76%) episodes among 2622 unvaccinated HCP and 226 (42.24%) episodes among 4823 vaccinated HCP (11.8 versus 4.7 episodes of absenteeism per 100 HCP, respectively; p-value < 0.001). The mean duration of absenteeism was 11.9 days among unvaccinated HCP compared with 6.9 days among vaccinated HCP (p-value < 0.001). Unvaccinated HCP more frequently developed acute respiratory infection, influenza-like illness, and COVID-19 (p-values < 0.001 for all comparisons). Vaccine effectiveness for fully vaccinated HCP was estimated at 94.16% [confidence interval (CI): 88.50%-98.05%) against COVID-19, 83.62% (CI: 73.36%-90.38%) against SARS-CoV-2 infection (asymptomatic or COVID-19), and 66.42% (CI: 56.86%-74.15%) against absenteeism. CONCLUSION: The COVID-19 pandemic had a considerable impact on healthcare workforce. The Pfizer-BioNTech vaccine significantly reduced morbidity, COVID-19, absenteeism and duration of absenteeism among HCP during a period of high SARS-CoV-2 circulation in the community. It is expected that HCP vaccination will protect them and healthcare services and contain healthcare costs.

Environmental testing for SARS-CoV-2 in three tertiary-care hospitals during the peak of the third COVID-19 wave.

Contamination of surfaces has been implicated in transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We tested by real-time PCR for SARS-CoV-2 contamination environmental samples from three hospitals during the peak of the third pandemic wave. Overall, 19 of 463 (4.1%) samples tested positive: 12 of 173 (6.9%) samples from a COVID-19 hospital, 3 of 177 (1.7%) samples from a non-COVID-19 hospital, and 4 of 113 (3.5%) samples from a pediatric hospital with dedicated COVID-19 clinics. Most positive samples originated from emergency departments (EDs) (47.3%) and the intensive care units (ICUs) (26.3%) of the COVID-19 hospital. Positive samples belonged almost exclusively (18/19) to the highly transmissible B.1.1.7 cluster, that might explain environmental contamination at this stage of the pandemic. The frequency and efficiency of disinfection in high-risk patient areas, such as EDs and ICUs, should be reinforced, especially during this period where highly transmissible variants of concern are widespread.

Transmission dynamics of SARS-CoV-2 within families with children in Greece: A study of 23 clusters.

There is limited information on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection clustering within families with children. We aimed to study the transmission dynamics of SARS-CoV-2 within families with children in Greece. We studied 23 family clusters of coronavirus disease 2019 (COVID-19). Infection was diagnosed by reverse-transcriptase polymerase chain reaction in respiratory specimens. The level of viral load was categorized as high, moderate, or low based on the cycle threshold values. There were 109 household members (66 adults and 43 children). The median attack rate per cluster was 60% (range: 33.4%-100%). An adult member with COVID-19 was the first case in 21 (91.3%) clusters. Transmission of infection occurred from an adult to a child in 19 clusters and/or from an adult to another adult in 12 clusters. There was no evidence of child-to-adult or child-to-child transmission. In total 68 household members (62.4%) tested positive. Children were more likely to have an asymptomatic SARS-CoV-2 infection compared to adults (40% vs 10.5%; P = .021). In contrast, adults were more likely to develop a severe clinical course compared with children (8.8% vs 0%; P = .021). In addition, infected children were significantly more likely to have a low viral load while adults were more likely to have a moderate viral load (40.7% and 18.6% vs 13.8% and 51.7%, respectively; P = .016). In conclusion, while children become infected by SARS-CoV-2, they do not appear to transmit infection to others. Furthermore, children more frequently have an asymptomatic or mild course compared to adults. Further studies are needed to elucidate the role of viral load on these findings.

Determinants of intention to get vaccinated against COVID-19 among healthcare personnel in hospitals in Greece.

BACKGROUND: To investigate intention rates to get vaccinated against COVID-19 among healthcare personnel (HCP) in Greece. METHODS: Cross-sectional survey. RESULTS: The response rate was 14.5%. Of 1521 HCP with a known profession, 607 (39.9%) were nursing personnel, 480 (31.6%) physicians, 171 (11.2%) paramedical personnel, 72 (4.7%) supportive personnel, and 191 (12.6%) administrative personnel. Overall, 803 of 1571 HCP (51.1%) stated their intention to get vaccinated while 768 (48.9%) stated their intention to decline vaccination. Most HCP (71.3%) who reported intent to get vaccinated noted contributing to the control of the pandemic and protecting their families and themselves as their reasons, while the most common reason for reporting intent to decline vaccination was inadequate information about the vaccines (74.9%), followed by concerns about vaccine safety (36.2%). Logistic regression analysis revealed that the probability of intending to get vaccinated increased with male gender, being a physician, history of complete vaccination against hepatitis B, history of vaccination against pandemic A (H1N1) in 2009-2010, belief that COVID-19 vaccination should be mandatory for HCP, and increased confidence in vaccines in general during the COVID-19 pandemic. The following factors were associated with a lower intention to get vaccinated: no vaccination against influenza the past season, no intention to get vaccinated against influenza in 2020-2021, and no intention to recommend COVID-19 vaccination to high-risk patients. CONCLUSION: There is an urgent need to built safety perception towards COVID-19 vaccines and raise vaccine uptake rates by HCP, and thus to protect the healthcare workforce and the healthcare services.

Children and Adolescents With SARS-CoV-2 Infection: Epidemiology, Clinical Course and Viral Loads.

BACKGROUND: There is limited information on severe acute respiratory syndrome virus 2 (SARS-CoV-2) infection in children. METHODS: We retrieved data from the national database on SARS-CoV-2 infections. We studied in-family transmission. The level of viral load was categorized as high, moderate, or low based on the cycle threshold values. RESULTS: We studied 203 SARS-CoV-2-infected children (median age: 11 years; range: 6 days to 18.4 years); 111 (54.7%) had an asymptomatic infection. Among the 92 children (45.3%) with coronavirus disease 2019 (COVID-19), 24 (26.1%) were hospitalized. Infants <1 year were more likely to develop COVID-19 (19.5% of all COVID-19 cases) (P-value = 0.001). There was no significant difference between viral load and age, sex, underlying condition, fever and hospitalization, as well as between type of SARS-CoV-2 infection and age, sex, underlying condition and viral load. Transmission from a household member accounted for 132 of 178 (74.2%) children for whom the source of infection was identified. An adult member with COVID-19 was the first case in 125 (66.8%) family clusters. Child-to-adult transmission was found in one occasion only. CONCLUSIONS: SARS-CoV-2 infection is mainly asymptomatic or mild during childhood. Adults appear to play a key role in spread of the virus in families. Most children have moderate or high viral loads regardless of age, symptoms or severity of infection. Further studies are needed to elucidate the role of children in the ongoing pandemic and particularly in light of schools reopening and the need to prioritize groups for vaccination, when COVID-19 vaccines will be available.