COVID-19 post-vaccination in healthcare workers and vaccine effectiveness, Brazil, 2021

Fernandes, Caio Medeiros; Dias, Shirley L.; Ferreira, Maira C.; Luna, Expedito J.A.

doi:10.1016/j.clinsp.2022.100109

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Sumário

Original articles • Clinics 77 • 2022 • https://doi.org/10.1016/j.clinsp.2022.100109 copy

COVID-19 post-vaccination in healthcare workers and vaccine effectiveness, Brazil, 2021

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Objects:

This study aimed to describe COVID-19 cases in healthcare workers at a large tertiary hospital, after a vaccination campaign, to understand the individual characteristics, timeliness, symptomatology, and severity of the conditions.

Methods:

The COVID-19 reporting files from the hospital’s healthcare workers and their records in the vaccine registry were analyzed, regarding vaccination status, symptoms, sociodemographic characteristics, comorbidities, and outcomes. Vaccination descriptive analysis was carried out and the impact and effectiveness of vaccination in relation to symptomatic infection and hospitalization were estimated.

Results:

In a total of 696 PCR-confirmed COVID-19 patients, vaccination coverage for the 1^st and 2^nd dose was 92.8% and 85.5%. Patients with complete doses had a mean interval of 96.8 days between vaccination and the onset of symptoms. Of the 664 participants with available clinical data, 165 had at least 1 comorbidity. During the study, 12 patients were hospitalized, 58.3% with a complete vaccination schedule. Three of this group died. The effectiveness of vaccination for symptomatic cases and hospitalization was 22.1% and 69.0%, respectively. The impact of vaccination on symptomatic cases and hospitalization was 81.4% and 89.7%, respectively.

Discussion:

The majority of COVID-19 cases in the study were classified as mild. The impact of vaccination for confirmed cases was significant, both in reducing the incidence of symptomatic cases and hospitalizations. The presence of comorbidities in approximately ¼ of the patients increased the risk of these individuals. The mean time interval between diagnosis and the 2^nd dose of vaccine was longer in the hospitalized group, reinforcing the protective decline over longer periods.

Keywords:
COVID-19; Clinical conditions; Healthcare workers; Vaccine effectiveness; Vaccine impact

HIGHLIGHTS

Vaccination with any vaccine was effective in preventing confirmed COVID-19 cases.

CoronaVac was effective in preventing COVID-19 related hospitalizations.

Vaccination had a significant impact in reducing cases and hospitalizations.

Predominance of mild cases, with respiratory symptoms, myalgia, and headache.

Vaccine protection waned over time.

Descriptors	Frequency (n)	Proportion (%)
Sex
Male	232	33.3
Female	464	66.7
Age group
16-29	168	24.1
30-39	181	26.0
40-49	173	24.9
50-59	119	17.1
60-78	55	7.9
Schooling
Elementary School	58	8.3
High School	218	31.3
University education	295	42.4
Missing	125	18.0
Race/Color
Yellow	12	1.7
White	517	74.3
Black	84	12.1
Missing	83	11.9
Total	696	100.0

Vaccine	Frequency (n)	Proportion (%)
1^st dose
Yes	646	92.8
No	49	7.1
Missing	1	0.1
Total	696	100.0
2^nd dose
Yes	595	85.5
No	98	14,0
Missing	3	0.5
Total	696	100.0

Age group	1^st dose		2^nd dose
	Yes	No	Yes	No
16–29	145 (86.8%)	22 (13.2%)	118 (70.7%)	49 (29.3%)
30–39	167 (92.3%)	14 (7.7%)	160 (88.4%)	21 (11.6%)
40–49	166 (96.0%)	7 (4.0%)	155 (90.6%)	16 (9.4%)
50–59	114 (95.8%)	5 (4.2%)	111 (93.3%)	8 (6.7%)
60–78	54 (98.2%)	1 (1.8%)	51 (92.7%)	4 (7.3%)
Total	646 (92.9%)	49 (7.1%)	595 (85.9%)	98 (14.1%)

Range of days	1^st dose	2^nd dose
15 or less	24 (3.8%)	27 (4.6%)
16–30	17 (2.7%)	65 (11.0%)
31–60	105 (16.4%)	86 (14.6%)
61–90	80 (12.5%)	94 (15.9%)
91–120	100 (15.7%)	115 (19.5%)
121–150	112 (17.5%)	78 (13.2%)
151–180	78 (12.2%)	54 (9.2%)
181–210	68 (10.6%)	67 (11.4%)
211–240	51 (8.0%)	1 (0.17%)
241 or more	4 (0.6%)	3 (0.51%)
Total	639 (100.0%)	590 (100.0%)

Symptom	Frequency	Proportion
Coryza	526	79.2%
Cough	516	77.7%
Headache	490	73.8%
Myalgia	387	58.3%
Sore throat	358	53.9%
Adynamia (weakness)	289	43.5%
Olfactory disorders	222	33.4%
Fever	213	32.1%
Taste disorders	176	26.5%
Nausea/vomiting	89	12.8%
Diarrhea	79	11.9%
Others	77	11.6%
Difficulty breathing	69	10.4%
Abdominal pain	20	3.0%
Musculoskeletal pain	25	3.7%
Gynecological complaints	2	0.3%
Rash	1	0.2%
Irritability/confusion	1	0.2%
Emotional disorders	–	0.0%

	2^nd dose of vaccine
Symptoms	Yes	No	p-value
Coryza			0.001
Yes	464 (81.5%)	62 (66.7%)
No	105 (18.5%)	31 (33.3%)
Adynamia (weakness)			0.001
Yes	233 (40.9%)	55 (59.1%)
No	336 (59.1%)	38 (40.9%)
Diarrhea			0.017
Yes	61 (10.7%)	18 (19.4%)
No	508 (89.3%)	75 (80.6%)
Myalgia			0.022
Yes	341 (59.9%)	44 (47.3%)
No	228 (40.1%)	49 (52.7%)
Nausea/Vomiting			0.029
Yes	69 (12.1%)	19 (20.4%)
No	500 (87.9%)	74 (79.6%)
Cough			0.162
Yes	447 (78.6%)	67 (72.0%)
No	122 (21.4%)	26 (28.0%)
Abdominal pain			0.182^a a Fisher’s Exact Test.
Yes	15 (2.6%)	5 (5.4%)
No	554 (97.4%)	88 (34.6%)
Difficulty breathing			0.204
Yes	55 (9.7%)	13 (14.0%)
No	514 (90.3%)	80 (86.0%)
Musculoskeletal pain			0.378^a a Fisher’s Exact Test.
Yes	20 (3.5%)	5 (5.4%)
No	548 (96.5%)	88 (94.6%)
Headach			0.535
Yes	417 (73.3%)	71 (76.3%)
No	152 (26.7%)	22 (23.7%)
Fever			0.595
Yes	180 (31.6%)	32 (34.4%)
No	389 (68.4%)	61 (65.6%)
Sore throat			0.678
Yes	305 (53.6%)	52 (55.9%)
No	264 (46.4%)	41 (44.1%)
Taste disorder			0.688
Yes	152 (26.7%)	23 (24.7%)
No	417 (73.3%)	70 (75.3%)
Olfactory disorder			0.830
Yes	190 (33.4%)	30 (32.3%)
No	379 (66.6%)	63 (67.7%)
Irritability/ Confusion			1.000^a a Fisher’s Exact Test.
Yes	1 (0.2%)	0 (0.0%)
No	568 (99.8%)	93 (100.0%)
Rash			1.000^a a Fisher’s Exact Test.
Yes	1 (0.2%)	0 (0.0%)
No	568 (99.8%)	93 (100.0%)
Gynecological complains			1.000^a a Fisher’s Exact Test.
Yes	2 (0.4%)	0 (0.0%)
No	567 (99.6%)	93 (100.0%)
Emotional disorders			–
Yes	0 (0.0%)	0 (0.0%)
No	569 (100.0%)	93 (100.0%)
Total	569 (100.0%)	93 (100.0%)	–

	Vaccinated (2 doses of any vaccine)	Unvaccinated
Population	21,590	3,852
Outpatient cases of COVID-19	563	129
Incidence	2.6%	3.4%
Effectiveness for COVID-19 cases	21.9% (95% CI 6.0%‒35.5%)
Hospitalized COVID-19 cases	7	4
Incidence	0.0324%	0.1038%
Effectiveness for hospitalization	68.8% (95% CI -6.6%‒90.9%)
	Vaccinated (2 doses of CoronaVac)	Unvaccinated
Population	21,542	3,846
Outpatient cases of COVID-19	547	92
Incidence	2.54%	2.39%
Effectiveness for COVID-19 cases	-6.3% (95% CI -17.2%‒24.3%)
Hospitalized COVID-19 cases	6	4
Incidence	0.0279%	0.1040%
Effectiveness for hospitalization	73.2% (95% IC 5.2%‒92.4%)

Timeline	March 2020 – February 2021	March 2021 – September 2021 Any vaccine (CoronaVac)
Number of cases	3,751	696 (639)
Incidence	14.7%	2.7% (2.52%)
Impact on incidence	81.4% (95% CI 79.9%‒82.9%)
	82.9% (95% CI 81.5%‒84.3%)
Hospitalized cases	106	11 (10)
Incidence	0.4166%	0.0432% (0.0394%)
Impact on hospitalization	89.6% (95% CI 80.7%‒94.4%)
	90.6% (95% CI 82.0%‒95.1%)

Faculdade de Medicina / USP Rua Dr Ovídio Pires de Campos, 225 - 6 and., 05403-010 São Paulo SP - Brazil, Tel.: (55 11) 2661-6235 - São Paulo - SP - Brazil
E-mail: clinics@hc.fm.usp.br

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[1] * Corresponding author. E-mail address: caio.medeiros@fm.usp.br (C.M. Fernandes).