Potential impact of two doses of SARS-CoV-2 vaccine on UK household transmission

In a recent study published in emerging infectious diseaseresearchers evaluated the impact of coronavirus disease 2019 (COVID-19) vaccination on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in households of UK residents.

Background

In a previous study, the authors of this study analyzed the HOSTED (Household Transmission Assessment Dataset) and identified SARS-CoV among unvaccinated household contacts of unvaccinated COVID-19 cases. -2 Observed a low probability of infection. In the case of an unvaccinated household contact of her unvaccinated COVID-19 case during a period when SARS-CoV-2 alpha variants predominate.

About research

In this study, investigators followed previous analyzes by assessing the effect of double-dose vaccination on transmission of SARS-CoV-2 to household contacts during the period when the delta variant was prevalent in the UK. extended.

HOSTED data confirmed by RT-PCR (reverse transcription polymerase chain reaction) analysis and data from COVID-19 cases reported to the National Surveillance System confirmed by LFD (lateral flow device) analysis were analyzed.

The HOSTED dataset was linked to data from the UK National Immunization Control System to extract information on type. [AstraZeneca’s ChAdOx1, Pfizer-BioNTech’s BNT162b2, or Moderna’s messenger ribonucleic acid (mRNA)-1273 (Moderna)], date and number of COVID-19 vaccinations administered. COVID-19 cases were linked to UPRNs (Unique Property Reference Numbers) through health records.

The results of the study were that household contacts of index cases who were vaccinated with two doses became secondary COVID-19 cases compared with index cases who were not vaccinated. Teams included only places consisting of 2 to her 10 residents. An index of household contacts of her COVID-19 case using sample collection data from 1 February 2021 to 13 September 2021 was included in the analysis.

A secondary COVID-19 case is described as a known household contact of an index case of COVID-19 with a SARS-CoV-2 positive report in a sample obtained 2 days to 2 weeks after the index case sample collection. I was. The team excluded institutions and living settings such as prisons and nursing homes. Cox regression modeling was used to calculate her HR (hazard ratio) after data adjustment for contact, socioeconomic status, and gender.

Households with a proband under the age of 16 in the United Kingdom (UK) Pillar 1 system consisted mostly of hospitalized patients, and households ineligible for COVID-19 vaccination were also excluded from the analysis. . Include only unvaccinated household contacts and by September 13, 2022, he will be tested for sensitivity by excluding COVID-19 unvaccinated individuals (probands or household contacts). performed the analysis.

result

Initially, the sample population consisted of index COVID-19 cases (n=1,779,448 individuals) from unique households (n=1,535,288 individuals) and household contacts (n=4,110,051 individuals). The team found 1,265,196 pediatric index COVID-19 cases, 99,627 UK Pillar 1 index cases, 785,669 co-prime index COVID-19 cases, and population We excluded households vaccinated before). In addition, individuals with uncertain vaccination status were excluded, resulting in 606,720 and 1,440,269 index cases and household contacts analyzed, respectively.

The median ages at first onset and contact were 35 and 32 years, respectively, and 51% and 49% of the corresponding participants were female. In total, 122,423 (9.0%) household contacts of secondary COVID-19 cases were analyzed. The majority of secondary COVID-19 cases were identified between February and May 2021, and most of the secondary COVID-19 cases were identified in households with index COVID-19 cases who were not vaccinated. rice field.

More secondary infections were observed among contacts of primary cases with ChAdOx1 vaccination and BNT162b2 vaccination, and among household contacts of primary COVID-19 cases who received ChAdOx1 vaccination since June. most secondary COVID-19 cases were observed in Secondary COVID-19 cases were consistently low among contacts of primary COVID-19 cases who received the mRNA-1273 vaccine, despite limited data being available.

The resulting HR values ​​were 0.2 for individuals residing in households with index cases of COVID-19 who received two doses of BNT162b2 vaccine and COVID-19 who received two doses of Ch4dOx1 vaccine during alpha-variant predominance. 0.5 for individuals living in households with index cases. , compared with unvaccinated contacts. The HRs obtained during periods of Delta variant predominance were 0.7 and 1.1 in BNT162b2 and Ch4dOx1 vaccinees, respectively. His COVID-19 case, indexing to test positive for SARS-CoV-2 more than 2.0 months after her second dose of either vaccine, showed less reduction in transmission of SARS-CoV-2. rice field.

Conclusion

Overall, the results of this study show that two doses of mRNA vaccination in index COVID-19 cases reduced the risk of SARS in unvaccinated household contacts during the delta variant predominance period compared with the alpha variant predominance period. – shown to reduce CoV-2 infection. A single dose of ChAdOx1 or mRNA vaccine reduced SARS-CoV-2 infection to a comparable extent, while the alpha variant predominated.

Furthermore, a decline in vaccine-conferred humoral immunity was observed over time. The findings of this study highlight the variation in vaccination-conferred immunity associated with SARS-CoV-2 transmission effects caused by emerging SARS-CoV-2 variants and reduced immune protection. The findings also highlight the need to monitor such impacts to guide the development of COVID-19 vaccination strategies.