Keywords
COVID-19 vaccines - adverse event - vaccine-preventable diseases - pregnant women
- Brazil
Palavras-chave
vacinas contra COVID-19 - evento adverso - doenças preveníveis por vacina - gestantes
- Brasil
Introduction
Since the beginning of the coronavirus disease 2019 (COVID-19) pandemic in December
2019, in China, up until February 2022, the world has seen multiple epidemic waves
leading to over 5.6 million deaths and 376 million confirmed cases worldwide.[1] Brazil has been particularly hit by the pandemic, accounting for over 628 thousand
deaths and 25.6 million cases until February 2022.[2]
Pregnant women and those in the postpartum period up to 45 days after delivery are
associated with higher risk for the development of severe disease caused by COVID-19,
including a higher risk of admission to the intensive care unit, need for mechanical
ventilation, and even death when compared to non-pregnant women of the same age. Additionally,
there is an increased risk for unfavorable obstetric outcomes resulting from the disease,
such as premature delivery and fetal death.[3]
[4] The mortality rates from COVID-19 was higher in pregnant women in Brazil than in
other countries, and by February 2022, 1,978 maternal deaths due to COVID-19 had been
confirmed in the country.[5]
The health, social, and economic crisis unleashed by the COVID-19 pandemic led to
massive investments in vaccine research, leading to the successful development of
a number of vaccines against the virus in record time. In December 2020, approximately
1 year after the virus was first identified, the World Health Organization (WHO) approved
the emergency use of the first COVID-19 vaccine. Presently, 10 different COVID-19
vaccines have been approved for clinical use by the World Health Organization (WHO),
including vaccines with new platforms, such as non-replicating viral vector vaccines
(AstraZeneca and Janssen) and messenger RNA (mRNA) vaccines (Pfizer/Wyeth and Moderna)
and consecrated platforms such as the aluminum-hydroxide-adjuvanted, inactivated whole
virus vaccine produced by Sinovac, the CoronaVac vaccine.
In Brazil, vaccination against COVID-19 started in January 2021. Considering the lack
of data regarding the safety and efficacy/effectiveness of COVID-19 vaccination in
pregnant and postpartum women, these groups were not included during the first phases
of the Brazilian vaccination strategy and were only included as a priority group after
extensive discussions about the risks and benefits. Regulations for the vaccination
of pregnant women in Brazil were published in the technical note of March 15, 2021,
from the Brazilian Ministry of Health (MoH).[6]
Despite the absence of robust data in the literature on the COVID-19 vaccinations
in pregnant women, it is understood that the benefit-risk ratio tends to be favorable
when considering the pandemic and the high burden of disease. Therefore, large-scale
use of these vaccines in pregnant women worldwide is justified. However, it is still
important to monitor for Events Supposedly Attributable to Vaccination or Immunization
(ESAVIs) and to draw safety profiles of the different platforms used in pregnant and
postpartum women.
The reporting of serious adverse events (SAEs) is mandatory in Brazil and any healthcare
professional which identifies a SAE is required to report the event to the National
Immunization Program (NIP) within 24 hours. Brazil has a well-established surveillance
system for ESAVIs, a partnership between the National Agency for Sanitary Surveillance
(Anvisa) and the NIP. After being notified, the adverse events are investigated by
local surveillance teams and evaluated for causality assessment.
Prior to the beginning of the COVID-19 vaccination strategy, the NIP adopted a new
online information system for the reporting of ESAVIs, e-SUS Notifica, which allows
for the notification of an ESAVI by any healthcare professional directly. Locations
with limited internet access are required to fill an ESAVI reporting form, which is
sent to a centralized center in order to be typed into the online system.
The present study aims at describing the main characteristics of ESAVIs related to
COVID-19 vaccines occurring in pregnant women and reported to the Brazilian NIP in
the first months of the vaccination campaign in Brazil.
Methods
This is a descriptive observational study of a case series of ESAVIs in pregnant women
reported between January 18 and August 1, 2021, in Brazil.
All cases of ESAVIs in pregnant women reported to the Brazilian MoH information system
for ESAVIs, e-SUS Notifica, between January 18 to August 1, 2021, in Brazil.
The definitions used are those recommended by the World Health Organization (WHO)[7] and described in the Brazilian Guidance for Epidemiological Surveillance of Adverse
Events Following Vaccination[8]:
-
1) Events Supposedly Attributable to Vaccination or Immunization (ESAVI): any unwanted
medical occurrences after vaccination, not necessarily causally related to the use
of a vaccine or other immunizing agents (immunoglobulins and heterologous serum).
An ESAVI can be any unwanted or unintended event, that is, symptom, disease, or abnormal
laboratory finding (WHO, 2016).[7]
-
2) Serious adverse event (SAE): any clinically relevant event that (i) requires hospitalization,
(ii) may compromise the patient, that is, cause risk of death and require immediate
clinical intervention to prevent death, (iii) causes significant dysfunction and/or
permanent incapacity, (iv) results in congenital anomaly, and (v) causes death.
-
3) Non-serious adverse event (NSAE): any other event that does not meet the SAE criteria.
-
4) Immunization error (programmatic): any avoidable event that can cause or lead to
inappropriate use of immunizing agents and/or harm to the patient.
-
5) Causality classification: A1 (vaccine product-related reaction [as per published
literature]), A2 (vaccine quality defect-related reaction ), A3 (immunization error-related
reaction), A4 (immunization anxiety-related reaction [ISRR]), B1 (temporal relationship
is consistent but there is insufficient definitive evidence for vaccine causing event
[may be new vaccine-linked event]), B2 (qualifying factors result in conflicting trends
of consistency and inconsistency with causal association to immunization), C (coincidental
underlying or emerging condition(s), or condition(s) caused by exposure to something
other than vaccine ), and D (unclassifiable).
For the present study, data related to ESAVIs such as: individual characteristics
(age, self-reported race, gestational age/trimester, comorbidities), vaccination data,
and ESAVI description data (dose type, vaccine type, place of vaccination, ESAVI classification
[severe, not severe], type of ESAVI) were extracted from the e-SUS Notifica information
system. All SAEs included were revised by medical doctors from the NIP.
Vaccination data (dose by vaccine type) was extracted from the National Network of
Health-Related Data (RNDS, in Portuguese) and National Immunization Program Information
System (SIPNI, in Portuguese).
To identify vaccinated pregnant women, the information regarding the priority group
for vaccination and the variables of pregnancy status identified in the SIPNI and
RNDS systems were considered. Data extracted from both systems were compiled in a
unified dataset and deduplicated. However, it should be noted that the variable for
pregnancy status was unavailable in the information systems at the beginning of the
vaccination campaign and was added as a variable during the campaign. Therefore, this
data does not represent the totality of vaccinated pregnant women and cannot be used
to calculate the direct incidence of ESAVI occurrence in this group.
Thus, the calculation of ESAVI incidence in the group of pregnant women was performed
after cross-referencing the individual taxpayer registry number (CPF) from the combined
vaccination database of vaccinated pregnant women (RNDS and SIPNI) and the ESAVI notification
data from “e-SUS Notifica”. This method allowed us to include only ESAVIS in pregnant
women with known pregnancy status on the vaccination information system as the numerator,
minimizing selection biases in the estimates of incidence. The incidence of events
was calculated per 100,000 doses administered. Additionally, data regarding ESAVIs
from the state of São Paulo in Brazil are not entered in “e-SUS Notifica”, hence data
regarding this state was not included in the analysis.
Data analysis was performed using descriptive statistics, with relative and absolute
frequency measurements. For data processing, the Pandas Library for Python version
1.1.3 was used, as well as the programs EpiInfo TM 7.2.3.1 and Microsoft Excel 2016
(Microsoft Corp., Redmond, WA, USA).
Ethical Aspects
This study was approved by the National Research Ethics Committee (CONEP) CAAE number
53592021.8.0000.0008. The criteria of confidentiality and non-disclosure of information
that could identify the individuals included in the databases were respected.
Results
During the evaluation period, 678,025 doses of COVID-19 vaccines administered to pregnant
women were registered (excluding the state of São Paulo), distributed as described
in [Table 1], with the Pfizer/Wyeth vaccine being the most widely administered vaccine (395,253
doses).
Table 1
Distribution of doses of vaccines against coronavirus disease 2019, applied in pregnant
women
|
Vaccine
|
First dose
|
Second dose
|
Total
|
|
AstraZeneca
|
56.362
|
5.966
|
62.328
|
|
Pfizer
|
386.077
|
9.176
|
395.253
|
|
Sinovac
|
140.651
|
77.795
|
218.446
|
|
Janssen
|
1.998
|
−
|
1.998
|
|
Total
|
585.088
|
92.937
|
678.025
|
In the same period, 1,674 notifications of ESAVIs in pregnant women were recorded
in e-SUS Notifica. After cross-referencing the data on vaccinated pregnant women and
ESAVIs data, 821 notifications were included for the analysis (231 immunization errors
and 582 adverse events), as represented in [Figure 1].
Fig. 1 Flowchart of Events Supposedly Attributable to Vaccination or Immunization (ESAVIs)
related to coronavirus disease 2019 (COVID-19) vaccines in pregnant women.
Of the 582 ESAVI-s identified, 481 (82%) were classified as NSAE, and 101 (18%) as
SAEs, 10 (9.9%) of which resulted in deaths ([Figure 1]). The incidence of SAEs was 14.9 per 100,000 doses administered. The vaccine with
the highest incidence of SAEs was the one by AstraZeneca, with 68.9 events per 100,000
doses, as described in [Table 2].
Table 2
Events Supposedly Attributable to Vaccination or Immunization in pregnant women according
to severity and vaccine type, reported to e-SUS Notifica
|
Adverse event
|
AstraZeneca
|
Pfizer
|
Sinovac
|
Janssen
|
Total
|
|
n
|
*Incid.
|
n
|
*Incid.
|
n
|
*Incid.
|
n
|
*Incid.
|
n
|
*Incid.
|
|
Serious
|
43
|
68.9
|
40
|
10.1
|
18
|
8.2
|
0
|
0.0
|
101
|
14.9
|
|
Death
|
3
|
4.8
|
4
|
1.0
|
3
|
1.4
|
0
|
0.0
|
10
|
1.5
|
|
Non-serious
|
342
|
548.7
|
103
|
26.1
|
35
|
16.0
|
1
|
50.1
|
481
|
70.9
|
|
Total
|
385
|
617.7
|
143
|
36.2
|
53
|
24.3
|
1
|
50.1
|
582
|
85.8
|
Abbreviation: Incid., number of reported events per 100 thousand doses administered.
The age distribution was similar among pregnant women in the three vaccination groups,
with the majority being between 20 and 34 years of age (438/582). The mean age was
also similar between the SAEs and NSAEs, with a mean of 29.5 and 27.7 years, respectively.
Most of the pregnant women's reported races were white (268/582), as self-declared
when using the notification system. The Southeast (212/582) and South (195/582) regions
accounted for most of the notifications ([Table 3]). Systemic arterial hypertension (SAH) and diabetes mellitus (DM) were the most
prevalent morbidities among pregnant women. Most ESAVis were reported during the 3rd trimester of pregnancy (51.4%), followed by the 2nd trimester (29.4%). Only 12 (2.1%) ESAVIs occurred after the 2nd dose ([Table 3]).
Table 3
Overall characteristics related to Events Supposedly Attributable to Vaccination or
Immunization
|
AstraZeneca (n = 385)
|
Pfizer
(n = 143)
|
Sinovac (n = 53)
|
Janssen (n = 1)
|
Total (n = 582)
|
|
n
|
%
|
n
|
%
|
n
|
%
|
n
|
%
|
n
|
%
|
|
Severity
|
|
|
|
|
|
|
|
|
|
|
|
Serious
|
43
|
11.2
|
40
|
28
|
18
|
34
|
0
|
0
|
101
|
17.4
|
|
Non serious
|
342
|
88.8
|
103
|
72.0
|
35
|
66
|
1
|
100
|
481
|
82.6
|
|
Age (years)
|
|
|
|
|
|
|
|
|
|
|
|
15–19
|
25
|
6.5
|
16
|
11
|
0
|
0
|
0
|
0
|
41
|
7.0
|
|
20–24
|
93
|
24.2
|
38
|
27
|
22
|
42
|
1
|
100
|
154
|
26.5
|
|
25–29
|
118
|
30.6
|
26
|
18
|
9
|
17
|
0
|
0
|
153
|
26.3
|
|
30–34
|
92
|
23.9
|
30
|
21
|
9
|
17
|
0
|
0
|
131
|
22.5
|
|
35–39
|
47
|
12.2
|
26
|
18
|
9
|
17
|
0
|
0
|
82
|
14.1
|
|
40–44
|
10
|
2.6
|
6
|
4.2
|
4
|
7.5
|
0
|
0
|
20
|
3.4
|
|
45–49
|
0
|
0.0
|
1
|
0.7
|
0
|
0
|
|
|
1
|
0.2
|
|
Self-reported skin color
|
|
|
|
|
|
|
|
|
|
|
|
White
|
184
|
47.9
|
61
|
43
|
23
|
44
|
0
|
0
|
268
|
46.0
|
|
Brown
|
141
|
36.6
|
46
|
32
|
25
|
47
|
1
|
100
|
213
|
36.6
|
|
Black
|
16
|
4.1
|
17
|
17
|
4
|
7.5
|
0
|
0
|
37
|
6.4
|
|
Yellow
|
1
|
0.2
|
1
|
0.7
|
0
|
0
|
0
|
0
|
2
|
0.3
|
|
Ignored
|
43
|
11.2
|
18
|
13
|
1
|
1.9
|
0
|
0
|
62
|
10.7
|
|
Regions
|
|
|
|
|
|
|
|
|
|
|
|
North
|
13
|
3.4
|
4
|
2.8
|
5
|
9.4
|
0
|
0
|
22
|
3.8
|
|
Northeast
|
67
|
17.4
|
23
|
16
|
3
|
5.6
|
0
|
0
|
93
|
16.0
|
|
Middle West
|
41
|
10.6
|
8
|
5.6
|
6
|
11
|
1
|
100
|
56
|
9.6
|
|
Southeast
|
130
|
33.7
|
68
|
47.5
|
18
|
34
|
0
|
0
|
216
|
37.1
|
|
South
|
134
|
34.8
|
40
|
28
|
21
|
40
|
0
|
0
|
195
|
33.5
|
|
Gestational age (trimester)
|
|
|
|
|
|
|
|
|
|
|
|
1° (0–12 weeks)
|
74
|
19.2
|
35
|
25
|
13
|
25
|
0
|
0
|
122
|
21.0
|
|
2° (13–23 weeks)
|
113
|
29.4
|
29
|
20
|
10
|
19
|
1
|
100
|
153
|
26.3
|
|
3° (24–40 weeks)
|
198
|
51.4
|
79
|
55
|
30
|
57
|
0
|
0
|
307
|
52.7
|
|
Previous conditions
|
|
|
|
|
|
|
|
|
|
|
|
Systemic arterial hypertension (SAH)
|
18
|
4.6
|
7
|
4.8
|
4
|
7.5
|
0
|
0
|
29
|
4.9
|
|
Diabetes mellitus (DM)
|
18
|
4.6
|
8
|
5.5
|
0
|
0
|
0
|
0
|
26
|
4.4
|
|
Obesity
|
2
|
0.0
|
4
|
2.8
|
0
|
0
|
0
|
0
|
6
|
1.5
|
|
More than one (SAH/DM/Obesity)
|
4
|
1.0
|
4
|
2.8
|
0
|
0
|
0
|
0
|
8
|
0.9
|
|
Asthma
|
6
|
1.5
|
4
|
2.8
|
1
|
2.3
|
0
|
0
|
11
|
1.3
|
|
Chronic kidney disease
|
1
|
0.2
|
0
|
0.2
|
0
|
0
|
0
|
0
|
1
|
0.2
|
|
Vaccine dose
|
|
|
|
|
|
|
|
|
|
|
|
1st dose
|
384
|
99.7
|
139
|
97.2
|
46
|
86.8
|
1
|
100
|
570
|
97.9
|
|
2nd dose
|
1
|
0.0
|
4
|
2.8
|
7
|
13
|
0
|
0
|
12
|
2.1
|
Unspecific systemic symptoms such as fever, myalgia, and headache were the most commonly
reported NSAEs (87.5%), mostly associated with the AstraZeneca vaccine (95%). Seven
cases of genital bleeding were reported among the NSAEs, all of which were considered
to be temporarily related to the vaccine but without sufficient evidence in the literature
to establish a causal relationship. Coronavirus disease 2019 infection was the most
frequently reported coincidental event ([Chart 1]).
Chart 1
Non severe Events Supposedly Attributable to Vaccination or Immunization against coronavirus
disease 2019 in pregnant women according to causality classification, event, and vaccine,
reported to e-SUS Notifica
|
Causality assessment
|
n
|
Adverse event
|
Vaccine
|
|
A.1- Vaccine product-related reaction (As per published literature)
|
6
|
Local reactions -Pain/erythema/edema
|
3 AstraZeneca
|
|
2 Pfizer
|
|
11
|
Exanthema/Rash/Pruritus
|
1 AstraZeneca
|
|
5 Pfizer
|
|
5 Sinovac
|
|
421
|
Unspecific systemic symptoms
(fever, myalgia, headache)
|
395 AstraZeneca
|
|
76 Pfizer
|
|
19 Sinovac
|
|
01 Janssen
|
|
3
|
Tachycardia/Hypertensive crisis
|
2 Pfizer
|
|
1 Sinovac
|
|
4
|
Abdominal pain
|
3 AstraZeneca
|
|
1 Sinovac
|
|
B.1 - Temporal relationship is consistent but there is insufficient definitive evidence
for vaccine causing event
|
7
|
Genital bleeding
|
2 AstraZeneca
|
|
2 Pfizer
|
|
3 Sinovac
|
|
C - Coincidental underlying or emerging condition(s), or condition(s) caused by exposure
to something other than vaccine
|
21
|
Covid-19
|
5 AstraZeneca
|
|
11 Pfizer
|
|
2 Sinovac
|
|
4
|
Urinary tract infections
|
2 Pfizer
|
|
2 AstraZeneca
|
|
1
|
Asthma
|
1 Pfizer
|
|
1
|
Deep venous thrombosis
|
1 AstraZeneca
|
|
2
|
Edema
|
1 Pfizer
|
|
1 Sinovac
|
During the evaluation period, 101 SAEs were reported, 43 (42.6%) after the AstraZeneca
vaccine, 40 (39.6%) after the Pfizer vaccine, and 18 (17.8%) after the Sinovac vaccine.
Infection by COVID-19 was the most frequent non-pregnancy-related adverse event, with
14 cases and 3 maternal deaths. Only one case of maternal death had a proven causal
relationship with vaccination (causality A1) and was secondary to thrombotic thrombocytopenic
syndrome (TTS) after the AstraZeneca/Fiocruz vaccine. The other nine maternal deaths
had causality C, that is, without causal relationship with the vaccine, and most were
due to complications inherent to pregnancy, such as pregnancy-specific hypertensive
disorder (PSHD) in 4 cases and 3 due to COVID-19 ([Table 4]). Pregnancy-related adverse events corresponded to most of the SAEs; the most frequent
being fetal death (26/101), with 3 of these cases classified as B1 and occurred in
the 3rd (14/26) and 2nd trimesters (12/26). First trimester abortion was the 2nd most prevalent (2/101) SAE, all with causality C, as shown in [Table 4].
Table 4
Severe Events Supposedly Attributable to Vaccination or Immunization against coronavirus
disease 2019 in pregnant women according to causality classification, diagnosis, and
vaccine
|
AstraZeneca (n = 43)
|
Pfizer
(n = 40)
|
Sinovac
(n = 18)
|
Total
(n = 101)
|
|
First trimester abortion
|
|
|
|
|
|
Causality C
|
9
|
12
|
3
|
24
|
|
Fetal death
|
|
|
|
|
|
Causality B1
|
1
|
2
|
0
|
26
|
|
Causality C
|
8
|
11
|
2
|
3
|
|
Causality D
|
0
|
1
|
1
|
220
|
|
Maternal death
|
|
|
|
|
|
Causality A1 (TTS*)
|
1
|
0
|
0
|
1
|
|
Causality C (4 PSHD*, 1 stroke, 1 coagulation disorders)
|
2
|
2
|
2
|
6
|
|
COVID-19
|
0
|
2
|
1
|
3
|
|
COVID-19
|
|
|
|
|
|
Causality C
|
5
|
5
|
4
|
14
|
|
Deep venous thrombosis (DVT)
|
|
|
|
|
|
Causality C
|
1
|
1
|
0
|
2
|
|
Stroke
|
|
|
|
|
|
Causality B1
|
0
|
1
|
1
|
2
|
|
Other neurologic conditions (seizure/facial palsy)
|
|
|
|
|
|
Causality B1
|
0
|
2
|
1
|
3
|
|
Immediate hypersensitivity reactions
|
|
|
|
|
|
Causality A1
|
0
|
2
|
1
|
3
|
|
Unspecific systemic symptoms
|
|
|
|
|
|
Causality A1
|
4
|
0
|
0
|
4
|
|
Genital bleeding
|
|
|
|
|
|
Causality B1
|
3
|
0
|
1
|
4
|
|
Preterm labor
|
|
|
|
6
|
|
Causality B1
|
2
|
0
|
0
|
2
|
|
Causality C
|
3
|
0
|
1
|
4
|
|
Amniotic fluid loss/oligohydramnios
|
|
|
|
|
|
Causality C
|
1
|
0
|
1
|
2
|
|
Pregnancy-specific hypertensive disorder (PSHD)
|
|
|
|
|
|
Causality C
|
1
|
0
|
0
|
1
|
|
Other diagnosis
|
|
|
|
|
|
Causality C
|
2
|
1
|
0
|
3
|
Abbreviations: A1, vaccine product-related reaction (as per published literature);
B1, temporal relationship is consistent but there is insufficient definitive evidence
for vaccine causing event (may be new vaccine-linked event); C, coincidental underlying
or emerging condition(s), or condition(s) caused by exposure to something other than
vaccine; D, unclassifiable; TTS, thrombocytopenic thrombotic syndrome; PSHD, pregnancy-specific
hypertensive disorder.
Discussion
The present study described the occurrence of ESAVIs in pregnant women vaccinated
against COVID-19 which were reported to e-SUS Notifica during the first 6 months of
the vaccination campaign in Brazil, including over 678 thousand vaccinated pregnant
women and 582 events. Most events were non serious (82.6%), although 10 deaths were
reported, and only 1 death was considered to be causally related to the vaccine.
The Southeast and South regions were responsible for ⅔ (70%) of the notifications
(excluding the state of São Paulo). The exclusion of the state of São Paulo was required
due to the adoption of a different notification system in that state. Such exclusion
led to the loss of an important dataset considering that it is the most populous state
in the country, with 46 million inhabitants as of 2020, and administered more than
35 million doses during the same period of the study.
In addition to the exclusion of the state of São Paulo, only the notifications of
women with confirmed pregnancy status in the vaccinated database were analyzed for
the consistent calculation of event incidences. This selection bias likely led to
an underrepresentation of pregnant women vaccinated during the first trimester, since
it is likely that these women were not aware of their pregnancy status when receiving
the vaccine.
The majority of our data correspond to the 1st vaccine dose since only 13.7% of the vaccinated individuals had received their 2nd dose during the analysis period. Likewise, only 12 events were reported after the
2nd dose, most of which were associated with the Sinovac vaccine (n = 7, 58.3%). This
is likely due to the different recommended intervals for each vaccine as indicated
by the NIP, which was initially 12 weeks for the AstraZeneca and Pfizer vaccines compared
with 28 days for the Sinovacas well as to the fact that pregnant women were only considered
a priority group from March 20, 2021.[9]
The AstraZeneca COVID-19 vaccine showed higher incidence of ESAVIs, 617.6 events per
100,000 doses administered in pregnant women, mostly non-severe unspecific systemic
symptoms. This higher incidence for the AstraZeneca vaccine was also observed in the
general population, 134.9 events per 100 thousand administered doses versus 92 events
for the Sinovac vaccine, as described in the special epidemiological bulletin[5] from the same period.
Most pregnant women were aged between 20 and 34 years (75% in the AstraZeneca and
Sinovac groups and 65% in the Pfizer group). The 3rd trimester was the most frequent trimester at the time of vaccine administration for
all vaccines. More than ⅔ of the described events (421/582) were due to unspecific
systemic symptoms, such as headache, myalgia, fever, and nausea, in all vaccines.
These are expected adverse events which had been previously described in clinical
trials by the manufacturers and are likely related to the vaccine itself. These data
are similar to recently published studies with mRNA[10] vaccines.
Coronavirus disease 2019 infection was the second most frequent NSAE, which reflects
the high risk of infection during the study period, making it likely that a proportion
of the NSAE which were reported due to undiagnosed COVID-19 cases. For the present
study a diagnosis of COVID-19 was made with a positive molecular or antigen tests
and those with descriptions of specific symptoms such as anosmia and/or dysgeusia,
according to the case definitions for COVID-19 adopted in the Brazilian Epidemiological
Surveillance Guide.[11] Limitations regarding testing availability in the 1st months of the pandemic likely led to an underestimation of the true number of COVID-19
cases in our study group.
Among the 101 SAE reported there were 10 cases of maternal deaths. Only one death
was classified as a vaccine product-related reaction according to WHO causality assessment
algorithm, resulting from a confirmed case of thrombocytopenic thrombotic syndrome
(TTS) related to the AstraZeneca vaccine. This led to an estimated incidence of 1.6
cases of TTS per 100,000 doses of AstraZeneca vaccine administered to pregnant women.
Such incidence is consistent with the incidence described in the general population
of roughly one case every 100,000 doses.[5] Thrombocytopenic thrombotic syndrome is an extremely rare syndrome which has been
described as likely caused by non-replicating adenoviral vaccines such as AstraZeneca
and Janssen. Despite its severity, it is generally understood that the risk-benefit
of vaccination is still highly favorable.
The incidence of SAEs post AstraZeneca vaccine was low, 68.9 per 100 thousand doses.
Although we do not use viral vector vaccine in our country, after these results it
seems to be plausible the vaccination with AstraZeneca in countries that do not have
other platforms available.
The other SAEs leading to maternal deaths were classified as “C,” being coincident
or inconsistent (i.e., they had causes other than the vaccine as triggering factors),
including 3 cases of COVID-19 initiating on the first few weeks immediately after
vaccination. These results strengthen our recommendation to vaccinate pregnant women,
especially due to the greater risk of complications inherent to the disease. A total
of 14 cases of severe COVID-19 were reported, amounting for 13.8% of the 101 SAEs.
Coronavirus disease 2019 infection was indeed responsible for the majority of the
non-obstetric events.
Among pregnancy-specific events, fetal death and first trimester abortion (up to the
13th week of pregnancy) were the most frequent SAEs, with an incidence of 3.8 and
3.5 cases per 100,000 doses, respectively. Spontaneous abortion, fetal death, and
premature birth are obstetric complications inherent to pregnancy. Systematic reviews
point to an expected gestational loss of around 15% for the total of confirmed[12] pregnancies. According to data extracted from the Brazilian National Information
System on Live Births (SINASC), Brazil had a 3.4% spontaneous abortion rate before
the COVID-19 pandemic and an 11% preterm birth rate per year.[13] Spontaneous abortion was also among the most frequent adverse events reported with
other vaccines such as influenza.[14] Our study period did not account for the entirety of the pregnancy duration, hence
it is not possible to draw direct comparisons; nevertheless, such low reporting rates
are likely within the expected.
Vaccination against COVID-19 was initiated in pregnant women, even in the absence
of clinical trials or robust safety data in literature. This recommendation was justified
mainly by the higher risk of hospitalizations, deaths, and obstetric complications
associated with the COVID-19 infection in pregnant women, that is, a favorable risk-benefit
ratio for vaccination. Additionally, the existence of preliminary phase 4 studies
with the Pfizer vaccine did not warn of adverse outcomes in vaccinated[10] pregnant women.
The occurrence of one case of TTS related to the AstraZeneca vaccine led to the interruption
of the use of adenoviral-vectored vaccines in pregnant women in Brazil. Although,
we understand that the occurrence of such case does not suggest an increased risk
of occurrence in pregnant women, considering that the incidence was within expected.
Also, in countries with low availability of alternative vaccine platforms for pregnant
women, it is likely that the use of adenoviral-vectored vaccines in this population
can be justified.
Conclusion
Events resulting in unfavorable obstetric outcomes for pregnant women or fetuses are
considered severe events of special interest, since data in literature are limited
in this population. Surveillance of these events, even if passive, is essential to
profile the safety of vaccines in pregnant women. Despite some limitations in our
study, we believe it brings new insights into COVID-19 vaccines in this group and
will add to the available evidence.
