🚨 Being “not up-to-date” on COVID-19 vaccination linked to lower risk of infection, study suggests 🌡️💉

Di United States Centers for Disease Control and Prevention (CDC) don update dia guidance on top coronavirus disease 2019 (COVID-19) vaccination for April 2023. All individuals above di age of six wey don collect at least one dose of a COVID-19 bivalent vaccine na im dem dey call “up-to-date” with COVID-19 vaccination. On di oda hand, individuals wey neva collect even one dose of a COVID-19 bivalent vaccine na im dem go call “not up-to-date” 😷📋

Recent research neva fit document di effectiveness of di bivalent vaccine, while di severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) XBB variants still dey circulate well well. Based on say dis viral variants still dey circulate, e dey make sense to ask if “up-to-date” individuals, wey get vaccine wey no sure if e dey effective, dey well protected against COVID-19 compared to dem wey no “up-to-date” 🤔💉💭

To address dis matter, one recent study wey dem post for di medRxiv* preprint server dey investigate if “not up-to-date” individuals get higher risk of COVID-19 pass “up-to-date” individuals.

About di study 📚🔬 Di current retrospective cohort study happen for Cleveland Clinic Health System (CCHS). Dem start to offer di COVID-19 bivalent messenger ribonucleic acid (mRNA) vaccine to dia employees on September 12, 2022. Di start date of dis study na January 23, 2023, wey be wen di XBB lineages first become di dominant circulating strains for Ohio.

Di study participants na CCHS employees for any location on September 12, 2022, wey still dey work wen di XBB lineages become dominant. Dem exclude individuals wey dem no get data about dia age and sex.

Di outcome variable na time to COVID-19, wey dem define as positive SARS-CoV-2 nucleic acid amplification test (NAAT). Dem closely monitor di study participants until May 10, 2023, wey allow dem evaluate di outcomes up to 100 days from di start of di study 📅🔍

Key findings 🔑📊 Dem consider total of 48,344 participants, but dem censor 1,445 because of termination of employment. For di study cohort, 12,841 pipo dey “up-to-date” on COVID-19 vaccination by di end of di study.

Out of dese individuals, 11,187 collect di Pfizer vaccine and 1,654 collect di Moderna vaccine. Total of 1,475 employees catch SARS-CoV-2 infection during di 100-day study period.

Di population dey relatively young, with mean age of 43 years. About 46% don get previous history of COVID-19 and 34% dey infected with di Omicron variant. Additionally, 87% of di study cohort don collect at least one vaccine dose and 92% don either get exposure to SARS-CoV-2 through infection or vaccination.

Di risk of COVID-19 dey lower for di “not up-to-date” group compared to di “up-to-date” group. When dem analyze tertiles of propensity to get tested for SARS-CoV-2 infection, di “not up-to-date” group no dey more likely to contract COVID-19.

Di classification for risk of COVID-19 dey better based on di prior infection status. Dem observe significantly lower risk of COVID-19 for individuals wey no dey much affected by di Omicron BQ or BA.4/BA.5 variants. However, dem no see clear difference between “up-to-date” and “not up-to-date” individuals when dem divide dem based on di most recent infection date 📊😷🔍

One reason why being “up-to-date,” based on di CDC definition, no dey associated with lower risk of COVID-19 na because di bivalent vaccine no too effective against di XBB lineages of di Omicron variant. Anoda reason fit be say di CDC definition no dey consider di protective effect of immunity wey pesin fit get from previous infection.

Conclusions 📝🔬 Di current study show say being “not up-to-date” on vaccination dey associated with lower risk of COVID-19 pass being “up-to-date.” Dis findings show di challenge wey dey to determine vaccine protection when di effectiveness reduce over time and di method of classifying risk based only on di receipt of vaccine wey no too sure if e dey effective 🤔💉😷

Di key strengths of dis study include di large sample size and say e happen for one country wey dey invest well for accurate tracking of di pandemic. Additionally, di methodology wey dem use to treat vaccination status as time-dependent covariate enable dem determine vaccine effectiveness for real time ⏰📈🔬

Di present study focus on all di infections wey dem detect and dem no separate between asymptomatic and symptomatic infections. Some asymptomatic and mildly symptomatic infections fit don pass dem by mistake, wey go make di information on previous COVID-19 infection incomplete.

Furthermore, dem no fit study if being “up-to-date” reduce di severity of di illness because severe illnesses dey rare. Lastly, because di study population dey young, dem no fit study di effects on immunocompromised individuals 📚🧑‍🔬🔍

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NOW IN ENGLISH

🚨 Being “not up-to-date” on COVID-19 vaccination linked to lower risk of infection, study suggests 🌡️💉

The United States Centers for Disease Control and Prevention (CDC) updated their guidance on coronavirus disease 2019 (COVID-19) vaccination in April 2023. All individuals above the age of six who had received at least one dose of a COVID-19 bivalent vaccine were considered to be “up-to-date” with COVID-19 vaccination. Conversely, individuals were considered to be not “up-to-date” if they had not received a single dose of a COVID-19 bivalent vaccine. 😷📋

Recent research has not been able to document the efficacy of the bivalent vaccine, while the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) XBB variants were the dominant circulating strains. Given that these viral variants remain the dominant circulating strains, it is reasonable to ask whether “up-to-date” individuals, with a vaccine of inconclusive effectiveness, are protected against COVID-19 as compared to their not “up-to-date” counterparts. 🤔💉💭

Addressing this issue, a recent study posted to the medRxiv* preprint server investigates whether not “up-to-date” individuals had a higher risk of COVID-19 than “up-to-date” individuals. 🔬🔍

About the study 📚🔬 The current retrospective cohort study was conducted at the Cleveland Clinic Health System (CCHS). The COVID-19 bivalent messenger ribonucleic acid (mRNA) vaccine was first offered to employees on September 12, 2022. The start date of this study was January 23, 2023, which was when XBB lineages first became the dominant circulating strains in Ohio.

Study participants were CCHS employees in any location on September 12, 2022, and remained employed when the XBB lineages became dominant. Individuals were excluded if their age and sex data were unavailable.

The outcome variable was time to COVID-19, which was defined as a positive SARS-CoV-2 nucleic acid amplification test (NAAT). The study participants were closely monitored until May 10, 2023, which allowed for the evaluation of outcomes up to 100 days from the inception of the study. 📅🔍

Key findings 🔑📊 A total of 48,344 participants were considered, 1,445 of whom were censored because of termination of employment. Within the study cohort, 12,841 were “up-to-date” on COVID-19 vaccination by the end of the study.

Of these individuals, 11,187 received the Pfizer vaccine and 1,654 received the Moderna vaccine. A total of 1,475 employees were infected with SARS-CoV-2 during the 100-day study period.

The population was relatively young, with a mean age of 43 years. About 46% had a previous history of COVID-19 and 34% were infected by the Omicron variant. Moreover, 87% of the study cohort received at least one vaccine dose and 92% were exposed to SARS-CoV-2 by infection or vaccination.

The risk of COVID-19 was lower in the “not up-to-date” group as compared to the “up-to-date” group. On analyzing tertiles of propensity to get tested for SARS-CoV-2 infection, the not “up-to-date” group was not more likely to contract COVID-19. 😷🔍

The classification for risk of COVID-19 was more appropriately provided by considering prior infection status. A significantly lower risk of COVID-19 was observed in individuals who were least affected by the Omicron BQ or BA.4/BA.5 variants. However, no clear difference was noted between “up-to-date” and “not up-to-date” individuals when stratified by the most recent infection date. 📊😷🔍

One reason why being “up-to-date,” based on the CDC definition, was not associated with a lower risk of COVID-19 was that the bivalent vaccine was less effective against the XBB lineages of the Omicron variant. Another reason could be that the CDC definition ignores the protective effect of immunity acquired from prior infection. 💉🤔😷

Conclusions 📝🔬 The current study reports that being not “up-to-date” on vaccination was associated with a lower risk of COVID-19 than being “up-to-date.” These findings demonstrate the challenges of gauging vaccine protection when efficacy wanes over time and the method of classifying risk is only based on the receipt of a vaccine of questionable effectiveness. 🤔💉😷

The key strengths of this study include its large sample size and that it was conducted in a country that devoted significant resources to accurately tracking the progression of the pandemic. Additionally, the methodology of treating vaccination status as a time-dependent covariate enabled the determination of vaccine efficacy in real-time. ⏰📈🔬

The present study focused on all detected infections and did not distinguish between asymptomatic and symptomatic infections. Several asymptomatic and mildly symptomatic infections could have been accidentally ignored, which would make information on prior COVID-19 incomplete.

Furthermore, the question of whether being “up-to-date” decreased the severity of illness could not be studied due to the rarity of severe illnesses. Lastly, owing to the young study population, the effects on immunocompromised subjects could not be studied. 📚🧑‍🔬🔍