Vaccine effectiveness against COVID-19 related hospital admission in the Netherlands by medical risk condition: A test-negative case-control study

INTRODUCTION

Vaccination remains crucial in reducing COVID-19 hospitalizations and mitigating the strain on healthcare systems. We conducted a multicenter study to assess vaccine effectiveness (VE) of primary and booster vaccination against hospitalization and to identify subgroups with reduced VE.

METHODS

From March to July 2021 and October 2021 to January 2022, a test-negative case-control study was conducted in nine Dutch hospitals. The study included adults eligible for COVID-19 vaccination who were hospitalized with respiratory symptoms. Cases tested positive for SARS-CoV-2 within 14 days prior to or 48 h after admission, while controls tested negative. Logistic regression was used to calculate VE, adjusting for calendar week, sex, age, nursing home residency and comorbidity. We explored COVID-19 case characteristics and whether there are subgroups with less effective protection by vaccination against COVID-19 hospitalization.

RESULTS

Between October 2021 to January 2022, when the Delta variant was dominant, 335 cases and 277 controls were included. VE of primary and booster vaccination was 78 % (95 % CI: 65-86), and 89 % (95 % CI: 69-96), respectively. Using data from both study periods, including 700 cases and 511 controls, VE of primary vaccination was significantly reduced in those aged 60+ and patients with malignancy, chronic cardiac disease or an immunocompromising condition.

CONCLUSION

Although VE against hospitalization was 78% and increased to 89% after boosting during the Delta-dominant study period, VE was lower in certain high risk groups, for which indirect protection or other protective measures might be of added importance.

Non-specific effects of the inactivated influenza vaccine. A test-negative study: The inactivated influenza vaccine and SARS-CoV-2 infections

BACKGROUND

Previous research suggested that the inactivated influenza vaccine (IIV) may protect against SARS-CoV-2 infection or a severe course of COVID-19. These findings were however based on cohort studies, that are prone to confounding by indication. We examined the association between IIV and SARS-Cov-2 infection in a Dutch population using a test-negative design.

METHODS

This test-negative case-control study was conducted in adults (≥60) who tested because of COVID-19 like symptoms at community SARS-CoV-2 testing locations in the Netherlands during the period of November 8th 2021-March 11th 2022. Information on receipt of IIV in October-November 2021 was routinely collected at each visit. Logistic regression was used to calculate unadjusted, partially (sex, age, education level) and fully adjusted (COVID-19 vaccination, IIV 2020) odds ratios (ORs) for receipt of IIV in SARS-CoV-2 positive versus negative subjects. Differential effects on SARS-CoV-2 risk by time since IIV were investigated by including an interaction term for calendar time: November 2021-January 2022 vs February-March 2022.

RESULTS

In total, 1,832 participants were included in the main analysis, of whom 336 (18.3 %) had a positive SARS-CoV-2 test. No significant association between IIV and SARS-CoV-2 infection was found; fully adjusted OR of 1.07 (95 % CI: 0.78-1.49). The interaction term for time periods was not significant (1.04 [95 % CI: 0.51-2.15], p = 0.91). Results were robust in sensitivity analyses.

CONCLUSIONS

While earlier observational studies suggested a protective non-specific effect of IIV and SARS-CoV-2 infections, this smaller, but well controlled test-negative design study does not suggest an effect, either positive or negative. Larger test-negative design studies, or alternative designs such as the self-controlled case series design are needed to confirm these findings and provide more definite answers on the topic.

Predicting the next pandemic: VACCELERATE ranking of the WorldHealth Organization's Blueprint forAction toPreventEpidemics

INTRODUCTION

The World Health Organization (WHO)'s Research and Development (R&D) Blueprint for Action to Prevent Epidemics, a plan of action, highlighted several infectious diseases as crucial targets for prevention. These infections were selected based on a thorough assessment of factors such as transmissibility, infectivity, severity, and evolutionary potential. In line with this blueprint, the VACCELERATE Site Network approached infectious disease experts to rank the diseases listed in the WHO R&D Blueprint according to their perceived risk of triggering a pandemic. VACCELERATE is an EU-funded collaborative European network of clinical trial sites, established to respond to emerging pandemics and enhance vaccine development capabilities.

METHODS

Between February and June 2023, a survey was conducted using an online form to collect data from members of the VACCELERATE Site Network and infectious disease experts worldwide. Participants were asked to rank various pathogens based on their perceived risk of causing a pandemic, including those listed in the WHO R&D Blueprint and additional pathogens.

RESULTS

A total of 187 responses were obtained from infectious disease experts representing 57 countries, with Germany, Spain, and Italy providing the highest number of replies. Influenza viruses received the highest rankings among the pathogens, with 79 % of participants including them in their top rankings. Disease X, SARS-CoV-2, SARS-CoV, and Ebola virus were also ranked highly. Hantavirus, Lassa virus, Nipah virus, and henipavirus were among the bottom-ranked pathogens in terms of pandemic potential.

CONCLUSION

Influenza, SARS-CoV, SARS-CoV-2, and Ebola virus were found to be the most concerning pathogens with pandemic potential, characterised by transmissibility through respiratory droplets and a reported history of epidemic or pandemic outbreaks.

Long term sequelae after SARS-CoV-2 infection in children: a household study

BACKGROUND

In children persistent symptoms after SARS-CoV-2 infection have been reported, however, duration and characteristics of symptoms in previously healthy children remain unclear. Therefore this study aimed to evaluate persisting symptoms in children at 6 and 12 months after a SARS-CoV-2 infection.

METHODS

In this prospective cohort study households with a confirmed SARS-CoV-2 positive outbreak were matched 1:1 to household controls from SARS-CoV-2 negative outbreaks. These households completed questionnaires at 6 and 12 months on the presence and severity of SARS-CoV-2 related symptoms, general well-being/functioning, cognition, persisting symptoms and quality of life.

FINDINGS

None of the children who had a SARS-CoV-2 infection during the study reported persistent symptoms at 6 and 12 months after infection, whereas almost 8% of the children with a negative RT-PCR test during the study reported symptoms such as coughing and mild fever, however, no significant differences were found. In addition, for all other outcomes, no differences were observed between the two groups.

TAKE HOME MESSAGE

Post-acute sequelae of mild SARS-CoV-2 infections appears to be uncommon in previously healthy children.

SARS-CoV-2 incidence in secondary schools; the role of national and school-initiated COVID-19 measures

INTRODUCTION

Our aim was to gain insight into the effect of COVID-19 measures on SARS-CoV-2 incidence in secondary schools and the association with classroom CO₂ concentration and airborne contamination.

METHODS

Between October 2020-June 2021, 18 schools weekly reported SARS-CoV-2 incidence and completed surveys on school-initiated COVID-19 measures (e.g. improving hygiene or minimizing contacts). CO₂ was measured in occupied classrooms twice, and SARS-CoV-2 air contamination longitudinally using electrostatic dust collectors (EDC) and analyzed using RT-qPCR. National COVID-19 policy measures varied during pre-lockdown, lockdown and post-lockdown periods. During the entire study, schools were recommended to improve ventilation. SARS-CoV-2 incidence rate ratios (IRR) were estimated by Generalized Estimating Equation (GEE) models.

RESULTS

During 18 weeks follow-up (range: 10-22) SARS-CoV-2 school-incidence decreased during national lockdown (adjusted IRR: 0.41, 95%CI: 0.21-0.80) and post-lockdown (IRR: 0.60, 0.39-0.93) compared to pre-lockdown. School-initiated COVID-19 measures had no additional effect. Pre-lockdown, IRRs per 10% increase in time CO₂ exceeded 400, 550 and 800 ppm above outdoor level respectively, were 1.08 (1.00-1.16), 1.10 (1.02-1.19), and 1.08 (0.95-1.22). Post-lockdown, CO_2-concentrations were considerably lower and not associated with SARS-CoV-2 incidence. No SARS-CoV-2 RNA was detected in any of the EDC samples.

CONCLUSION

During a period with low SARS-CoV-2 population immunity and increased attention to ventilation, with CO₂ levels most of the time below acceptable thresholds, only the national policy during and post-lockdown of reduced class-occupancy, stringent quarantine, and contact testing reduced SARS-CoV-2 incidence in Dutch secondary schools. Widespread SARS-CoV-2 air contamination could not be demonstrated in schools under the prevailing conditions during the study.

SARS-CoV-2 outbreaks in secondary school settings in the Netherlands during fall 2020; silent circulation

BACKGROUND

In fall 2020 when schools in the Netherlands operated under a limited set of COVID-19 measures, we conducted outbreaks studies in four secondary schools to gain insight in the level of school transmission and the role of SARS-CoV-2 transmission via air and surfaces.

METHODS

Outbreak studies were performed between 11 November and 15 December 2020 when the wild-type variant of SARS-CoV-2 was dominant. Clusters of SARS-CoV-2 infections within schools were identified through a prospective school surveillance study. All school contacts of cluster cases, irrespective of symptoms, were invited for PCR testing twice within 48 h and 4-7 days later. Combined NTS and saliva samples were collected at each time point along with data on recent exposure and symptoms. Surface and active air samples were collected in the school environment. All samples were PCR-tested and sequenced when possible.

RESULTS

Out of 263 sampled school contacts, 24 tested SARS-CoV-2 positive (secondary attack rate 9.1%), of which 62% remained asymptomatic and 42% had a weakly positive test result. Phylogenetic analysis on 12 subjects from 2 schools indicated a cluster of 8 and 2 secondary cases, respectively, but also other distinct strains within outbreaks. Of 51 collected air and 53 surface samples, none were SARS-CoV-2 positive.

CONCLUSION

Our study confirmed within school SARS-CoV-2 transmission and substantial silent circulation, but also multiple introductions in some cases. Absence of air or surface contamination suggests environmental contamination is not widespread during school outbreaks.

Longitudinal Household Assessment of Respiratory Illness in Children and Parents During the COVID-19 Pandemic

IMPORTANCE

In the early COVID-19 pandemic, SARS-CoV-2 testing was only accessible and recommended for symptomatic persons or adults. This restriction hampered assessment of the true incidence of SARS-CoV-2 infection in children as well as detailed characterization of the SARS-CoV-2 disease spectrum and how this spectrum compared with that of other common respiratory illnesses.

OBJECTIVE

To estimate the community incidence of SARS-CoV-2 infection in children and parents and to assess the symptoms and symptom severity of respiratory illness episodes involving SARS-CoV-2-positive test results relative to those with SARS-CoV-2-negative test results.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study randomly selected Dutch households with at least 1 child younger than 18 years. A total of 1209 children and adults from 307 households were prospectively followed up between August 25, 2020, and July 29, 2021, covering the second and third waves of the COVID-19 pandemic. Participation included SARS-CoV-2 screening at 4- to 6-week intervals during the first 23 weeks of participation (core study period; August 25, 2020, to July 29, 2021). Participants in all households finishing the core study before July 1, 2021, were invited to participate in the extended follow-up and to actively report respiratory symptoms using an interactive app until July 1, 2021. At new onset of respiratory symptoms or a SARS-CoV-2 positive test result, a household outbreak study was initiated, which included daily symptom recording, repeated polymerase chain reaction testing (nose-throat swabs and saliva and fecal samples), and SARS-CoV-2 antibody measurement (paired dried blood spots) in all household members. Outbreaks, households, and episodes of respiratory illness were described as positive or negative depending on SARS-CoV-2 test results. Data on participant race and ethnicity were not reported because they were not uniformly collected in the original cohorts and were therefore not representative or informative.

EXPOSURES

SARS-CoV-2-positive and SARS-CoV-2-negative respiratory illness episodes.

MAIN OUTCOMES AND MEASURES

Age-stratified incidence rates, symptoms, and symptom severity for SARS-CoV-2-positive and SARS-CoV-2-negative respiratory illness episodes.

RESULTS

Among 307 households including 1209 participants (638 female [52.8%]; 403 [33.3%] aged <12 years, 179 [14.8%] aged 12-17 years, and 627 [51.9%] aged ≥18 years), 183 household outbreaks of respiratory illness were observed during the core study and extended follow-up period, of which 63 (34.4%) were SARS-CoV-2 positive (59 outbreaks [32.2%] during the core study and 4 outbreaks [2.2%] during follow-up). SARS-CoV-2 incidence was similar across all ages (0.24/person-year [PY]; 95% CI, 0.21-0.28/PY). Overall, 33 of 134 confirmed SARS-CoV-2 episodes (24.6%) were asymptomatic. The incidence of SARS-CoV-2-negative respiratory illness episodes was highest in children younger than 12 years (0.94/PY; 95% CI, 0.89-0.97/PY). When comparing SARS-CoV-2-positive vs SARS-CoV-2-negative respiratory illness episodes in children younger than 12 years, no differences were observed in number of symptoms (median [IQR], 2 [2-4] for both groups), symptom severity (median [IQR] maximum symptom severity score, 6 [4-9] vs 7 [6-13]), or symptom duration (median [IQR], 6 [5-12] days vs 8 [4-13] days). However, among adults, SARS-CoV-2-positive episodes had a significantly higher number (median [IQR], 6 [4-8] vs 3 [2-4]), severity (median [IQR] maximum symptom severity score, 15 [9-19] vs 7 [6-11]), and duration (median [IQR] 13 [8-29] days vs 5 [3-11] days; P < .001 for all comparisons) of symptoms vs SARS-CoV-2-negative episodes.

CONCLUSIONS AND RELEVANCE

In this cohort study, during the first pandemic year when mostly partial or full in-person learning occurred, the SARS-CoV-2 incidence rate in children was substantially higher than estimated from routine testing or seroprevalence data and was similar to that of adult household members. Unlike in unvaccinated adults, SARS-CoV-2 symptoms and symptom severity in children were similar to other common respiratory illnesses. These findings may prove useful when developing pediatric COVID-19 vaccine recommendations.

Vaccine effectiveness against COVID-19 related hospital admission in the Netherlands: a test-negative case-control study

Introduction

Real-world vaccine effectiveness (VE) estimates are essential to identify potential groups at higher risk of break-through infections and to guide policy. We assessed the VE of COVID-19 vaccination against COVID-19 hospitalization, while adjusting and stratifying for patient characteristics.

Methods

We performed a test-negative case-control study in six Dutch hospitals. The study population consisted of adults eligible for COVID-19 vaccination hospitalized between May 1 and June 28, 2021 with respiratory symptoms. Cases were defined as patients who tested positive for SARS-CoV-2 by PCR during the first 48 h of admission or within 14 days prior to hospital admission. Controls were patients tested negative at admission and did not have a positive test during the 2 weeks prior to hospitalization. VE was calculated using multivariable logistic regression, adjusting for calendar week, sex, age, comorbidity and nursing home residency. Subgroup analysis was performed for age, sex and different comorbidities. Secondary endpoints were ICU-admission and mortality.

Results

379 cases and 255 controls were included of whom 157 (18%) were vaccinated prior to admission. Five cases (1%) and 40 controls (16%) were fully vaccinated (VE: 93%; 95% CI: 81 – 98), and 40 cases (11%) and 70 controls (27%) were partially vaccinated (VE: 70%; 95% CI: 50–82). A strongly protective effect of vaccination was found in all comorbidity subgroups. No ICU-admission or mortality were reported among fully vaccinated cases. Of unvaccinated cases, mortality was 10% and 19% was admitted at the ICU.

Conclusion

COVID-19 vaccination provides a strong protective effect against COVID-19 related hospital admission, in patients with and without comorbidity.

Transmission of SARS-CoV-2 within households: a remote prospective cohort study in European countries

Household transmission studies are useful to quantify SARS-CoV-2 transmission dynamics. We conducted a remote prospective household study to quantify transmission, and the effects of subject characteristics, household characteristics, and implemented infection control measures on transmission. Households with a laboratory-confirmed SARS-CoV-2 index case were enrolled < 48 h following test result. Follow-up included digitally daily symptom recording, regular nose-throat self-sampling and paired dried blood spots from all household members. Samples were tested for virus detection and SARS-CoV-2 antibodies. Secondary attack rates (SARs) and associated factors were estimated using logistic regression. In 276 households with 920 participants (276 index cases and 644 household members) daily symptom diaries and questionnaires were completed by 95%, and > 85% completed sample collection. 200 secondary SARS-CoV-2 infections were detected, yielding a household SAR of 45.7% (95% CI 39.7–51.7%) and per-person SAR of 32.6% (95%CI: 28.1-37.4%). 126 (63%) secondary cases were detected at enrollment. Mild (aRR = 0.57) and asymptomatic index cases (aRR = 0.29) were less likely to transmit SARS-CoV-2, compared to index cases with an acute respiratory illness (p = 0.03 for trend), and child index cases (< 12 years aRR = 0.60 and 12-18 years aRR = 0.85) compared to adults (p = 0.03 for trend). Infection control interventions in households had no significant effect on transmission. We found high SARs with the majority of transmissions occuring early after SARS-CoV-2 introduction into the household. This may explain the futile effect of implemented household measures. Age and symptom status of the index case influence secondary transmission. Remote, digitally-supported study designs with self-sampling are feasible for studying transmission under pandemic restrictions.

[Rotavirus vaccination for all Dutch infants]

Recently, the Netherlands Health Council (HC) issued an updated advice on rotavirus vaccination. Rotavirus gastro-enteritis primarily affects young children, of whom, in the Netherlands, annually ~2700 end up in the hospital and 5-7 die. In 2017, the HC judged positively on rotavirus vaccination of young children, but also concluded that the cost-effectiveness of general vaccination was unfavorable. Yet, the HC recommended to at least vaccinate vulnerable children in specific risk-groups. Because of the corona crisis, this, however, has not materialized. Meanwhile, the Dutch Risk-group Infant Vaccination Against Rotavirus study has demonstrated that rotavirus vaccination of children in risk-groups is less effective than previously thought. Therefore, the HC now recommends rotavirus vaccination of all children. General vaccination within the Dutch NIP is expected to result in herd-immunity, such that all children, including those in risk-groups, are protected. Nonetheless, the Dutch Ministry of Health has decided to postpone implementation of rotavirus vaccination.

Experiences and needs of persons living with a household member infected with SARS-CoV-2: A mixed method study

BACKGROUND

Households are important sites for transmission of SARS-CoV-2 and preventive measures are recommended. This study aimed to 1) investigate the impact of living with a person infected with SARS-CoV-2; 2) understand how household members implemented infection control recommendations in their home; and 3) identify the information and support needs of household members.

METHODS

For this observational mixed-methods study, households with a person with confirmed SARS-CoV-2 infection were recruited via drive-through testing sites of Municipal Health Services, healthcare worker screening or hospital emergency visits in the University Medical Centre Utrecht, the Netherlands and via primary care physicians, hospital emergency visits or preoperative screening in the University Hospital of Antwerp, Belgium. We recorded household characteristics, including characteristics of all household members, together with their views on prevention measures. In a subset of households one adult household member was asked to participate in an interview investigating their views on preventive measures. Survey data were analysed using descriptive statistics and interview data by rapid framework analysis. A triangulation protocol was used to integrate findings.

RESULTS

Thirty-four households (120 household members) were included in the quantitative survey. Twenty-two households were invited to be interviewed, of which 18 completed an interview (response 81.8%). Survey data showed that almost all households implemented some preventive measures, the use of face masks being least frequently reported. Measures taken depended on what was physically possible, the perceived severity of illness of the index patient and to what extent household members were willing to limit social interaction. Respondents did not believe in the effectiveness of wearing face masks within the house, and from the interviews this was explained by media coverage of face masks, impracticality and the stigma associated with wearing masks. Interviewees reported that quarantine had a high emotional burden and wished to have more information about the exact duration of quarantine, their own COVID-19 status, symptoms and when to seek medical help.

CONCLUSION

People were willing to implement prevention measures, however actual adherence depended on perceived severity of illness and the perceived risk of becoming infected. Homes are social environments and recommendations for infection prevention should account for this context. Incorporating our findings into policy making could provide households with more relevant and actionable advice.

Cost-effectiveness of inactivated influenza vaccination in children with medical risk conditions in the Netherlands

BACKGROUND

In many countries, annual immunization with inactivated influenza vaccine (IIV) is recommended for children with medical risk conditions. Prior cost-effectiveness analyses found such immunization to be cost saving, but assumed effectiveness against non-severe influenza outcomes and a higher effectiveness against severe influenza outcomes than recent studies would suggest. However, recent vaccine studies do not indicate any reduction in community or outpatient disease episodes in IIV immunized individuals. We therefore evaluated cost-effectiveness of IIV immunization in children with medical risk conditions in the Netherlands, assuming that IIV reduces influenza-related hospitalization and death, but has no meaningful impact on non-severe health outcomes.

METHODS

A health economic decision tree model was developed to evaluate health effects and costs of annual IIV immunization versus no immunization. Model inputs were based on our study on influenza-related primary care visits and other literature. Immunization was considered cost effective if associated costs were less than €20,000 per quality-adjusted life year (QALY) gained. Probabilistic sensitivity analyses were performed to assess robustness of results, and one-way sensitivity analyses and scenario analyses were done to assess the influence of individual parameters.

RESULTS

Annual IIV prevents an average of 1.59 influenza-related hospitalizations and 0.02 deaths per 1,000 children with medical risk conditions. This results in an expected QALY gain of 0.43 at incremental costs of €21,564 per 1,000 children, corresponding to an incremental cost-effectiveness ratio (ICER) of €50,297/QALY compared to no immunization. Under base case assumptions, immunization had a 5% probability of being cost effective. Results were most influenced by vaccine efficacy against fatal influenza, QALY loss due to death, and mortality rate.

CONCLUSIONS

If IIV only reduces severe disease outcomes, as current evidence suggests, annual immunization of medical risk children is unlikely to be cost effective. Results should however be interpreted with caution as cost-effectiveness is largely dependent on incidence and QALY losses for fatal influenza, for which evidence is scarce.

Increased Carotid Intima-Media Thickness in Children with a History of Dengue Hemorrhagic Fever

We assessed carotid intima-media thickness (cIMT) and arterial stiffness in 28 children and adolescents with previous dengue hemorrhagic fever (DHF) (mean interval between DHF and cardiovascular assessment, 8.4 years), and 34 controls in a low-resource setting. Participants with previous DHF had an adjusted increased cIMT of 42.6 µm (95% confidence interval [CI]: 10.0-75.3, P = 0.01), and 61.7 µm (95% CI: 21.5-102.0, P < 0.01) in a subgroup analysis on dengue shock syndrome. There were no differences in arterial stiffness. In this first exploratory study, children and adolescents with a history of DHF had an increased cIMT, which may be modulated by dengue severity.

[Advisory statement of the Health Council of the Netherlands on vaccination against meningococcal disease: a missed opportunity?]

The recent outbreak of serogroup W meningococcal disease in the Netherlands, and the start of the vaccination campaign for adolescents in response, dominated the national headlines in 2018. During this time, the Health Council of the Netherlands prepared an advisory statement, which was released in December 2018, on how meningococcal disease caused by various serogroups could be controlled in the future. The Counsel recommends to include vaccination against serogroups A, C, W and Y for infants and adolescents in the Dutch National Immunization Programme. By contrast, vaccination against serogroup B was not recommended. This article is a commentary on the recommendations in the advisory statement and discusses the epidemiology of meningococcal serogroup B infections in the Netherlands, the effectiveness of the vaccine against this serogroup as well as common side effects, and as such demonstrates the difficult balance between pros and cons and the need for broadly based discussion in the public sphere about the scope of the Dutch National Immunization Programme.

Impact of Repeated Influenza Immunization on Respiratory Illness in Children With Preexisting Medical Conditions

PURPOSE

Annual influenza immunization in medical risk groups is recommended in many countries. Recent evidence suggests that repeated inactivated influenza vaccine (IIV) immunization throughout childhood may impair long-term immunity against influenza. We assessed whether prior immunization altered the effect of IIV in children with preexisting medical conditions on primary care-diagnosed respiratory illness (RI) episodes during the influenza season.

METHODS

Electronic records of IIV-immunized children who met the criteria for annual IIV immunization according to Dutch guidelines were extracted from a primary care database from 2004 to 2015. For each year, we collected information on IIV immunization status, primary care-attended RI episodes (including influenza-like illness, acute RI, and asthma exacerbation), and potential confounders. Generalized estimating equations were used to model the association between prior IIV and occurrence of at least one RI episode during the influenza season, with "current year immunized but without IIV history" as reference group.

RESULTS

A total of 4,183 children (follow-up duration: 11,493 child-years) were IIV immunized at least once. Adjusted estimates showed lower odds for RI in current year-immunized children with prior IIV compared with those without (odds ratio [OR] = 0.61; 95% CI, 0.47-0.78 for "current year immunized and one IIV in previous 2 years"; OR = 0.85; 95% CI, 0.68-1.07 for "current year immunized and ≥2 IIVs in previous 3 years, including prior year").

CONCLUSION

Repeated IIV immunization in children with preexisting medical conditions has no negative impact on, and may even increase, long-term protection against RI episodes diagnosed during the influenza season in primary care.

[Rotavirus vaccination: a priority for high-risk children]

Rotaviruses cause acute gastroenteritis; mostly in young children. Infant rotavirus vaccines have been licensed in Europe and provide excellent protection against severe gastroenteritis, but are not widely implemented due to the perceived benign character of rotavirus disease and unfavourable cost-effectiveness. Rotavirus vaccines are currently unavailable in the Netherlands which leaves a particularly vulnerable group of infants--those with prematurity, low birth weight or severe congenital malformations--at increased risk of rotavirus disease, complications and even death. Rotavirus vaccination should be made available to these infants, but due to the strict age limits for the rotavirus vaccination (which must be started at < 14 weeks), vaccination cannot be adequately organised within the Dutch National Immunisation Programme (NIP) which relies on well-baby clinic visits. Organising rotavirus vaccination for high-risk infants through paediatric secondary care could overcome this problem and be implemented independent of decisions on uptake of rotavirus vaccination within the Dutch NIP.