tetano
Editor, Senior Moderator
Open Forum Infect Dis
. 2022 Apr 15;9(5)
fac178.
doi: 10.1093/ofid/ofac178. eCollection 2022 May.
SARS-CoV-2 mRNA Vaccine Effectiveness in Health Care Workers by Dosing Interval and Time Since Vaccination: Test-Negative Design, British Columbia, Canada
Shiraz El Adam[SUP] 1 [/SUP], Macy Zou[SUP] 2 [/SUP], Shinhye Kim[SUP] 1 [/SUP], Bonnie Henry[SUP] 3 4 [/SUP], Mel Krajden[SUP] 5 6 [/SUP], Danuta M Skowronski[SUP] 1 3 [/SUP]
Affiliations
Abstract
Background: One- and two-dose mRNA vaccine effectiveness (VE) estimates against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection by dosing interval and time since vaccination were assessed among healthcare workers (HCWs) in publicly funded acute and community (nonresidential) healthcare facilities in British Columbia, Canada.
Methods: A test-negative design was used with controls matched to cases (6:1) on epidemiological week of SARS-CoV-2 test date. mRNA vaccination was defined by receipt of the first dose ≥21 days or second dose ≥14 days before the test date. HCWs ≥18 years old tested for SARS-CoV-2 between epi-weeks 3 and 39 (January 17-October 2, 2021) were included, when varying dosing intervals and a mix of circulating variants of concern contributed, including Delta dominance provincially from epi-week 31 (August 1).
Results: Single- and two-dose analyses included 1265 and 1246 cases, respectively. The median follow-up period (interquartile range) was 49 (34-69) days for single-dose and 89 (61-123) days for two-dose recipients, with 12%, 31%, and 58% of second doses given 3-5, 6, or ≥7 weeks after the first. Adjusted mRNA VE against SARS-CoV-2 was 71% (95% CI, 66%-76%) for one dose and 90% (95% CI, 88%-92%) for two doses, similar to two heterologous mRNA doses (92%; 95% CI, 86%-95%). Two-dose VE remained >80% at ≥28 weeks post-second dose. Two-dose VE was consistently 5%-7% higher with a ≥7-week vs 3-5-week interval between doses, but with overlapping confidence intervals.
Conclusions: Among HCWs, we report substantial single-dose and strong and sustained two-dose mRNA vaccine protection, with the latter maintained for at least 7 months. These findings support a longer interval between doses, with global health and equity implications.
Keywords: 2; CoV; SARS; healthcare workers; negative design; test; vaccine effectiveness.
. 2022 Apr 15;9(5)
fac178.doi: 10.1093/ofid/ofac178. eCollection 2022 May.
SARS-CoV-2 mRNA Vaccine Effectiveness in Health Care Workers by Dosing Interval and Time Since Vaccination: Test-Negative Design, British Columbia, Canada
Shiraz El Adam[SUP] 1 [/SUP], Macy Zou[SUP] 2 [/SUP], Shinhye Kim[SUP] 1 [/SUP], Bonnie Henry[SUP] 3 4 [/SUP], Mel Krajden[SUP] 5 6 [/SUP], Danuta M Skowronski[SUP] 1 3 [/SUP]
Affiliations
- PMID: 35531384
- PMCID: PMC9047244
- DOI: 10.1093/ofid/ofac178
Abstract
Background: One- and two-dose mRNA vaccine effectiveness (VE) estimates against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection by dosing interval and time since vaccination were assessed among healthcare workers (HCWs) in publicly funded acute and community (nonresidential) healthcare facilities in British Columbia, Canada.
Methods: A test-negative design was used with controls matched to cases (6:1) on epidemiological week of SARS-CoV-2 test date. mRNA vaccination was defined by receipt of the first dose ≥21 days or second dose ≥14 days before the test date. HCWs ≥18 years old tested for SARS-CoV-2 between epi-weeks 3 and 39 (January 17-October 2, 2021) were included, when varying dosing intervals and a mix of circulating variants of concern contributed, including Delta dominance provincially from epi-week 31 (August 1).
Results: Single- and two-dose analyses included 1265 and 1246 cases, respectively. The median follow-up period (interquartile range) was 49 (34-69) days for single-dose and 89 (61-123) days for two-dose recipients, with 12%, 31%, and 58% of second doses given 3-5, 6, or ≥7 weeks after the first. Adjusted mRNA VE against SARS-CoV-2 was 71% (95% CI, 66%-76%) for one dose and 90% (95% CI, 88%-92%) for two doses, similar to two heterologous mRNA doses (92%; 95% CI, 86%-95%). Two-dose VE remained >80% at ≥28 weeks post-second dose. Two-dose VE was consistently 5%-7% higher with a ≥7-week vs 3-5-week interval between doses, but with overlapping confidence intervals.
Conclusions: Among HCWs, we report substantial single-dose and strong and sustained two-dose mRNA vaccine protection, with the latter maintained for at least 7 months. These findings support a longer interval between doses, with global health and equity implications.
Keywords: 2; CoV; SARS; healthcare workers; negative design; test; vaccine effectiveness.