Table. Effectiveness of two and three doses of mRNA vaccines against SARI COVID-19 hospitalisations among individuals without previous COVID-19 diagnosisa, during Omicron predominance, by age group and time since last dose, Slovenia, February–March 2022.
| Age group (years) | Individuals vaccinated with two dosesb | Individuals vaccinated with three dosesb | Unvaccinated individualsc | Vaccine effectiveness | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Individuals vaccinated with two dosesb | Individuals vaccinated with three dosesb | ||||||||||||
| Number of SARI COVID-19 casesd | Population vaccinated with two dosesb | Rate per 100,000 | Number of SARI COVID-19 casesd | Population vaccinated with three dosesb | Rate per 100,000 | Number of SARI COVID-19 casesd | Unvaccinated population | Rate per 100,000 | % | 95% CI | % | 95% CI | |
| Irrespective of the last dose timing | |||||||||||||
| 18–49 | 11 | 124,922 | 8.8 | 5 | 60,627 | 8.3 | 44 | 154,167 | 28.5 | 69 | 40–84 | 71 | 27–89 |
| 50–64 | 42 | 63,231 | 66.4 | 8 | 83,781 | 9.6 | 163 | 66,685 | 244.4 | 73 | 62–81 | 96 | 92–98 |
| ≥ 65 | 275 | 61,019 | 450.7 | 261 | 225,199 | 115.9 | 641 | 26,031 | 2,462.4 | 82 | 79–84 | 95 | 95–96 |
| Last dose ≤ 3 months ago | |||||||||||||
| 18–49 | 2 | 21,429 | 9.3 | 5 | 55,020 | 9.1 | 44 | 154,167 | 28.5 | 67 | 0–92 | 68 | 20–87 |
| 50–64 | 14 | 8,445 | 165.8 | 3 | 72,696 | 4.1 | 163 | 66,685 | 244.4 | 32 | 0–61 | 98 | 95–99 |
| ≥ 65 | 38 | 9,181 | 413.9 | 133 | 142,585 | 93.3 | 641 | 26,031 | 2,462.4 | 83 | 77–88 | 96 | 95–97 |
| Last dose 4–5 months ago | |||||||||||||
| 18–49 | 4 | 37,322 | 10.7 | 0 | 4,718 | 0.0 | 44 | 154,167 | 28.5 | 62 | 0–87 | 100 | ND |
| 50–64 | 4 | 17,503 | 22.9 | 5 | 10,109 | 49.5 | 163 | 66,685 | 244.4 | 91 | 75–97 | 80 | 51–92 |
| ≥ 65 | 79 | 16,925 | 466.8 | 124 | 78,438 | 158.1 | 641 | 26,031 | 2,462.4 | 81 | 76–85 | 94 | 92–95 |
| Last dose ≥ 6 months ago | |||||||||||||
| 18–49 | 5 | 66,172 | 7.6 | 0 | 889 | 0.0 | 44 | 154,167 | 28.5 | 74 | 33–90 | 100 | ND |
| 50–64 | 24 | 37,283 | 64.4 | 0 | 976 | 0.0 | 163 | 66,685 | 244.4 | 74 | 60–83 | 100 | ND |
| ≥ 65 | 158 | 34,913 | 452.6 | 4 | 4,177 | 95.8 | 641 | 26,031 | 2,462.4 | 82 | 78–85 | 96 | 90–99 |
CI: confidence interval; COVID-19: coronavirus disease; mRNA: messenger ribonucleic acid; ND: not determined (95% CIs were not determined for all VE estimates of 100%); SARI: severe acute respiratory infection; SARS-CoV-2: severe acute respiratory syndrome coronavirus 2.
a Individuals without previous COVID-19 diagnosis were defined as individuals without a record of a positive SARS-CoV-2 PCR (or only a positive RAT from 21 December 2020 to 12 February 2021 and from 1 February 2022 to 27 March 2022) in the national COVID-19 database more than 2 weeks before the week under observation within the SARI surveillance database known as EPISARI [3].
b Individuals vaccinated with two or three doses were defined as individuals who had received two or three doses of mRNA vaccines (Comirnaty (BNT162b2 mRNA, BioNTech-Pfizer, Mainz, Germany/New York, United States) or Spikevax (mRNA-1273, Moderna, Cambridge, United States)) more than 2 weeks before the week under observation.
c Unvaccinated individuals were defined as individuals who had not received any dose of any vaccine against COVID-19.
d SARI COVID-19 cases were defined as all SARI cases testing positive for SARS-CoV-2 by PCR or antigen test at admission to hospitals.
Data sources: EPISARI surveillance of severe acute respiratory infections within comprehensive COVID-19 surveillance [3], national electronic registry of vaccinated individuals and adverse events following vaccinations [4], national COVID-19 dataset and Slovenian Central Population Registry.