Characteristics of the omicron XBB subvariant wave in Singapore

Goh, Alvin Xie Cheng; Chae, Sae-Rom; Chiew, Calvin J; Tang, Nicole K. Y.; Pang, Deanette; Chen, Lin; Tan, Kelvin Bryan; Lee, Vernon J; Ho, Zheng Jie Marc

doi:10.1016/s0140-6736(23)00390-2

Cited by 18 publications

(23 citation statements)

References 2 publications

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“…This requires further study as we used a predetermined Omicron XBB community circulation period (October 2022 to April 2023) rather than wholegenome sequencing of confirmed cases in the analysis. 25 Previous studies primarily looked at VE from receipt of vaccination during pregnancy. Pregnant people who received vaccination prior to pregnancy was an exclusion criterion in the Canadian study.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, we identified in our Omicron XBB variant–specific analysis the need for a third dose (booster) during pregnancy for the lower risk of infection to be maintained. This requires further study as we used a predetermined Omicron XBB community circulation period (October 2022 to April 2023) rather than whole-genome sequencing of confirmed cases in the analysis …”

Section: Discussionmentioning

confidence: 99%

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mRNA SARS-CoV-2 Vaccination Before vs During Pregnancy and Omicron Infection Among Infants

Goh,

Pang,

Tan

et al. 2023

JAMA Netw Open

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ImportanceInfants younger than 6 months are at risk of severe SARS-CoV-2 infection. Data are lacking on the optimum timing for maternal vaccination and estimated effectiveness against Omicron variants, including XBB, for infants.ObjectiveTo investigate maternal vaccination against Omicron variants, including XBB, and the association of vaccination timing during pregnancy vs prior to pregnancy and risks of SARS-CoV-2 infection among infants aged 6 months or younger.Design, Setting, and ParticipantsThis population-based cohort study was conducted between January 1, 2022, and March 31, 2023. Singapore’s national dataset was used to study infants born at greater than 32 weeks’ gestation between January 1, 2022, and September 30, 2022. The study included infants whose parents had a confirmed SARS-CoV-2 infection from the date of birth up to 6 months of age. Of 21 609 infants born during this period, 7292 (33.7%) had at least 1 parent infected with SARS-CoV-2 before the age of 7 months. Statistical analysis was performed from April to July 2023.ExposureInfants’ mothers were unvaccinated, vaccinated prior to pregnancy, or vaccinated with a messenger RNA (mRNA) SARS-CoV-2 vaccine during pregnancy.Main Outcome and MeasureInfants were considered infected if they had a positive polymerase chain reaction test.ResultsAmong 7292 infants included in this study, 4522 (62.0%) had mothers who were Chinese, 527 (7.2%) had mothers who were Indian, 2007 (27.5%) had mothers who were Malay, and 236 (3.2%) had mothers who were other ethnicity; 6809 infants (93.4%) were born at full term, and 1272 infants (17.4%) were infected during the study period. There were 7120 infants (97.6%) born to mothers who had been fully vaccinated or boosted as of 14 days prior to delivery. The crude incidence rate was 174.3 per 100 000 person-days among infants born to mothers who were unvaccinated, 122.2 per 100 000 person-days among infants born to mothers who were vaccinated before pregnancy, and 128.5 per 100 000 person-days among infants born to mothers who were vaccinated during pregnancy. The estimated vaccine effectiveness (VE) was 41.5% (95% CI, 22.8% to 55.7%) among infants born to mothers vaccinated during pregnancy. Infants of mothers who received vaccination prior to pregnancy did not have a lower risk for infection (estimated VE, 15.4% [95% CI, −17.6% to 39.1%]). A lower risk for Omicron XBB infection was only observed among mothers vaccinated with the third (booster) dose antenatally (estimated VE, 76.7% [95% CI, 12.8% to 93.8%]).Conclusions and RelevanceIn this population-based cohort study, maternal mRNA vaccination was associated with a lower risk of Omicron SARS-CoV-2 infection among infants up to 6 months of age only if the vaccine was given during the antenatal period. These findings suggest that mRNA vaccination during pregnancy may be needed for lower risk of SARS-CoV-2 infection among newborns.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mRNA SARS-CoV-2 Vaccination Before vs During Pregnancy and Omicron Infection Among Infants

Goh,

Pang,

Tan

et al. 2023

JAMA Netw Open

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“…In Singapore, the monovalent mRNA-1273 (Moderna) and BNT162b2 (Pfizer-BioNTech) vaccines were approved for children aged 6 months to 4 years in August 2022 and September 2022, respectively . From October 2022, community transmission in Singapore surged due to the emergence of Omicron XBB . Omicron XBB remained the predominant subvariant (≥50% of community cases) throughout the end of 2022 and early 2023 .…”

Section: Introductionmentioning

confidence: 99%

“…From October 2022, community transmission in Singapore surged due to the emergence of Omicron XBB . Omicron XBB remained the predominant subvariant (≥50% of community cases) throughout the end of 2022 and early 2023 . In March 2023, another surge in community transmission was attributed to a mix of XBB sublineages (XBB 1.5/XBB 1.9/XBB 1.16) that accounted for 90% or more of cases on genomic surveillance .…”

Section: Introductionmentioning

confidence: 99%

Effectiveness of Monovalent mRNA Vaccines Against Omicron XBB Infection in Singaporean Children Younger Than 5 Years

Wee,

Tang,

Pang

et al. 2023

JAMA Pediatr

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ImportanceLiterature on vaccine effectiveness of SARS-CoV-2 messenger RNA (mRNA) vaccines for children younger than 5 years is limited.ObjectiveTo report the effectiveness of monovalent mRNA vaccines against SARS-CoV-2 infection among Singaporean children aged 1 through 4 years during a COVID-19 pandemic wave of the Omicron XBB variant.Design, Setting, and ParticipantsThis was a population-based cohort study, conducted over a 6-month study period from October 1, 2022, through March 31, 2023, after the implementation of community vaccination among all Singaporean children aged 1 through 4 years. The study period was dominated by the Omicron XBB subvariant.ExposureReceipt of SARS-CoV-2 mRNA vaccines.Main Outcome MeasureVaccine effectiveness against confirmed SARS-CoV-2 infection. The adjusted incidence rate ratio for confirmed infections using Poisson regression was reported, with the reference group being those who were unvaccinated. Analyses were stratified by prior documented SARS-CoV-2 infection.ResultsA total of 121 628 children (median [IQR] age, 3.1 [2.2-3.9] years; 61 925 male [50.9%]) were included in the study, contributing 21 015 956 person-days of observation. The majority of children (11 294 of 11 705 [96.5%]) received the mRNA-1273 COVID-19 vaccine (Moderna). Vaccine effectiveness against confirmed infection was 45.2% (95% CI, 24.7%-60.2%) in partially vaccinated, infection-naive children and 63.3% (95% CI, 40.6%-77.3%) in fully vaccinated, infection-naive children compared with the unvaccinated group. Among previously infected children, vaccine effectiveness against reinfections in those with at least 1 vaccine dose was estimated at 74.6% (95% CI, 38.7%-89.5%).Conclusions and RelevanceStudy results suggest that completion of a primary mRNA vaccine series provided protection against SARS-CoV-2 infection in children aged 1 through 4 years. Although incidence of hospitalization and severe illness is low in this age group, there is potential benefit of vaccination in preventing infection and potential sequelae.

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“…XBB lineages have a remarkable growth advantage over other omicron variants, such as BA.5 and BA.2.75. Once it enters the population, the XBB lineage spreads and becomes predominant much more quickly than other variants 7. XBB lineages are one of the most immune evasive subvariants, causing an increase in reinfections 8.…”

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confidence: 99%