Πρωτότυπα επιστημονικών μελετών σχετικά με τον SARS-CoV-2

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Εδώ παρατίθενται μόνο αυτούσιες επίκαιρες μελέτες σχετικά με τον SARS-CoV-2.

Για προσωπικές απόψεις, απόψεις τηλεπερσόνων, σπασμένα τηλέφωνα - παρερμηνείες με ποπ άρθρα, ξεκάθαρες διαστρεβλώσεις που απευθύνονται σε αμόρφωτους και καθυστερημένους, κλπ σκουπιδαριό, δόξα το θεό υπάρχουν όλα τα υπόλοιπα νήματα του φόρουμ.

[Προέλλην]

Οι πιθανότητα να πάθει κάποιος Long Covid ενώ είναι (πλήρως) εμβολιασμένος, εφόσον έχει πάραυτα μολυνθεί (breakthrough infection), είναι οι μισές απ ότι εάν δεν είναι (πλήρως) εμβολιασμένος.

Risk factors and disease profile of post-vaccination SARS-CoV-2 infection in UK users of the COVID Symptom Study app: a prospective, community-based, nested, case-control study

September 01, 2021

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Discussion

We present data on 6030 and 2370 community-based adults in the UK with test-confirmed SARS-CoV-2 infection after their first or second COVID-19 vaccinations, respectively, with BNT162b2, ChAdOx1 nCoV-19, or mRNA-1273. Participants were included if they tested positive for SARS-CoV-2 at least 14 days after their first vaccination or at least 7 days after their second vaccination when immunity had developed32
and infection was unlikely to be due to exposure around the time of vaccination (eg, when travelling to the vaccination centre).

We found that the odds of having symptoms for 28 days or more after post-vaccination infection were approximately halved by having two vaccine doses. This result suggests that the risk of long COVID is reduced in individuals who have received double vaccination, when additionally considering the already documented reduced risk of infection overall.

Almost all individual symptoms of COVID-19 were less common in vaccinated versus unvaccinated participants, and more people in the vaccinated than in the unvaccinated groups were completely asymptomatic. This increased incidence of asymptomatic or minimally symptomatic infection in vaccinated participants underlines the importance of individuals who interact with unvaccinated or clinically vulnerable groups (eg, health-care workers and social care workers) continuing to regularly take tests for SARS-CoV-2, even if vaccinated, in line with current UK testing guidelines.33
We also found that COVID-19 was less severe (both in terms of the number of symptoms in the first week of infection and the need for hospitalisation) in participants after their first or second vaccine doses compared with unvaccinated participants. We have previously shown that having more than five symptoms in the first week of infection was associated with COVID-19 severity20
and disease duration.21

Frailty was associated with post-vaccination infection in older adults following their first vaccine dose, highlighting the need for ongoing caution in this clinically vulnerable group. The association was consistent in our sensitivity analysis using inverse probability weighting for factors influencing vaccination, but not after adjusting for potential confounders such as local area deprivation and lifestyle. This increased risk might therefore reflect increased exposure: unlike non-frail older adults, frail older adults might require carer visits or attendance at health-care facilities. Frail adults in long-term care facilities are at particular risk of transmitting respiratory illness, and have been disproportionately affected throughout the COVID-19 pandemic.17 Another explanation for this result concerns altered immune function (immunosenescence), a well established feature of physiological ageing.34, 35 The increased odds of post-vaccination infection in frail older adults could be compounded by the more severe outcomes of COVID-19 in this group, including delirium25 and death;17 indeed, in our study, 23% of frail, older adults testing positive for SARS-CoV-2 after their first vaccination presented to hospital. Systematic frailty screening in acute and community-based settings might facilitate differential, targeted re-vaccination scheduling, appropriate isolation precautions, case detection, testing, and proactive care, as recommended in guidance published by the National Institute for Health and Care Excellence36
and National Health Service (NHS) England.37

Research on augmenting immunogenicity in frail individuals is needed, such as on the impact and timing of booster vaccinations.

We found an inverse association of age with the odds of post-vaccination infection, especially in older adults. This finding is consistent with a previous study in non-vaccinated individuals showing lower anti-SARS-CoV-2 antibody seroprevalence in older adults (≥65 years) compared with younger adults (35–44 years),38 perhaps reflecting shielding in this age group in accordance with the classification of individuals older than 70 years as clinically vulnerable. Our study found some evidence to suggest that kidney disease might increase the odds of SARS-CoV-2 infection in older adults after their first vaccine dose, which is notable given that individuals with kidney disease were under-represented in the phase 2 and phase 3 trials of the COVID-19 vaccines.39

However, this finding should be interpreted cautiously because of the relatively small numbers of participants with kidney disease in this study. This increased risk of post-vaccination infection for people with kidney disease could reflect increased exposure (eg, when attending dialysis appointments) or impaired immunogenicity, and is supported by a study looking at humoral and B-cell responses in vaccinated, immunosuppressed kidney transplant recipients and patients having dialysis.40

Several other comorbidities, including heart disease and lung disease, were significantly associated with post-vaccination infection after one dose in older adults; although associations of marginal significance should be interpreted cautiously, many of these comorbidities confer a higher risk of severe disease, hospitalisation, mechanical ventilation, and mortality from COVID-19,16, 18 and ongoing shielding behaviours could be influencing our results to reduce the strength of these associations.
Greater area-level deprivation was associated with increased odds of SARS-CoV-2 infection after a single vaccine dose, consistent with findings from the pre-vaccination era.15

This association persisted following further adjustment for compliance with infection control guidance (ie, mask wearing). Factors associated with increased area-level deprivation include higher population density and more ethnic diversity, which are in themselves associated with increased mortality from COVID-19.18

More deprived areas might have lower vaccination coverage for COVID-19,41 and our finding might reflect increased viral transmission. Our results suggest that health policies to mitigate infection might need to specifically target these areas. Conversely, individuals without obesity had a lower odds of infection following their first vaccine dose. This finding suggests that immune responses post-vaccination might be influenced by obesity, although unadjusted confounding remains a possibility.

Our observation of differences by vaccine type agrees with real-world UK data on the effectiveness of ChAdOx1 nCoV-19 and BNT162b2 against the delta variant (B.1.617.2);42, however, our observation should be treated cautiously given the confounding factors influencing the vaccine type administered in different age groups and demographics. We emphasise that our study is observational, rather than a formal comparison.

Our study has some limitations. Although we used data from a large population of individuals reporting on a mobile phone app, the sample contained disproportionately more women than men and under-represented individuals in more deprived areas. Furthermore, we were unable to analyse the impact of ethnicity due to the low number of participants who provided this information, and our findings might not apply at all timepoints post-vaccination, to settings with different proportions of SARS-CoV-2 variants, or to countries with a different vaccination schedule.

Additionally, the data were self-reported; recording of comorbidities, test results, and vaccination status might not have been completely accurate and there might have been temporal gaps in reporting. Users of the COVID Symptom Study app are asked to log daily; therefore, if a participant reports on alternate days, the proportion of missing daily entries is 50%. However, given the typical duration of COVID-19 symptoms, the sampling frequencies in the COVID Symptom Study should have allowed good characterisation of infections.

Our study has strengths. Previous data from the COVID Symptom Study have concurred well with population-based COVID-19 studies,44
including on the influence of sociodemographic factors.15

The mobile phone data collection method allows the collection of daily prospective information on a comprehensive set of symptoms, permitting the analysis of both individual symptoms and overall illness duration (although necessary data censoring could have underestimated symptom duration in both cases and controls, as some individuals only had 2 weeks of logging after their positive test result).

The design of our study, including matching cases and controls for health-care worker status and the date of the post-vaccination test, reduced the potential for bias, although small differences between the groups remained on matched variables. We acknowledge the potential differences in logging by vaccinated individuals or those undertaking regular testing (eg, required for work as a health-care worker). Access to testing is a potential source of bias: as of July, 2021, RT-PCR is recommended for symptomatic individuals and a LFAT is recommended for asymptomatic individuals in the UK.33

The risk of reporting a positive SARS-CoV-2 test is higher among frontline health-care workers than among the general population,14
probably reflecting increased exposure and testing. After the first vaccine dose, positive tests were by RT-PCR in a higher proportion of vaccinated cases than in unvaccinated controls. Because RT-PCR is used for symptomatic testing in the UK, this would bias away our finding of a higher likelihood of asymptomatic or minimally symptomatic COVID-19 in vaccinated versus unvaccinated participants. However, there is uncertainty due to the high numbers of unvaccinated controls who reported an unknown test type after their first vaccine dose.

Our data suggest that the risk of post-vaccination SARS-CoV-2 infection is reduced in older age groups. To examine the effect of age on post-vaccination infection, we did not match controls 1 and controls 2 by age. However, age was included as a covariate in all analyses other than that looking at the effect of age itself, and stratified analyses are presented for younger and older age groups. Although vaccination itself might be considered a potential index event bias, the population of interest in this study was the vaccinated population, and findings should not be construed as applying to those who are unvaccinated. The UK adopted a vaccine prioritisation strategy starting with older age groups, so older adults were more likely to be vaccinated in this study than were younger adults.45

We examined and found no evidence of event bias on the basis of the probability of being vaccinated. Analyses in this study were not corrected for multiple testing, and so observations of marginal significance should be interpreted cautiously.

Frailty was assessed with the PRISMA-7 questionnaire. This assessment correlates well with other frailty measures46
and has the advantage of focusing on the functional consequences of frailty, which are not routinely captured in health records. However, PRISMA-7 has only been validated in older adults; results in younger adults should be interpreted cautiously.24

To conclude, the odds of post-vaccination infection following the first dose were increased in frail, older adults and in those living in more deprived areas, and were decreased in individuals without obesity. Compared with unvaccinated controls, after their second vaccine dose, individuals were less likely to have prolonged illness (symptoms for ≥28 days), more than five symptoms in the first week of illness, or present to hospital. Most symptoms were less common in vaccinated versus unvaccinated participants. Fully vaccinated individuals with COVID-19, especially if they were 60 years or older, were more likely to be completely asymptomatic than were unvaccinated controls. This finding might support caution around relaxing physical distancing and other personal protective measures in the post-vaccination era, particularly around frail older adults and individuals living in more deprived areas, even if these individuals are vaccinated. Our findings might also have implications for strategies such as booster vaccinations.

Κώδικας: Επιλογή όλων

https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(21)00460-6/fulltext