In a real-world research conducted in Israel, two doses of the Pfizer/BioNTech COVID-19 vaccine were found to be safe and 78 percent efficient in avoiding infection in expectant mothers.
The retrospective, observational study, which was conducted by researchers at Maccabi Healthcare Services in Tel Aviv, was published in the journal JAMA yesterday. It required evaluating data from 15,060 women who were enrolled in a pregnancy registry of a big, state-mandated healthcare system and who had a first dose of the vaccine between December 19, 2020, and February 28, 2021.
Using age, gestational age, residential region, demographic subgroup, number of times they had given birth, and flu vaccination status (a proxy for health-seeking behaviour), the women were matched 1:1 with unvaccinated pregnant women, and they were monitored until April 11, 2021.
Risk dropped in vaccinees over time
Among the 7,530 vaccinated women, 118 (1.6 percent) were infected with SARS-CoV-2 at least 28 days after receiving their first dose of the BNT162b2 vaccine, compared to 202 (2.7 percent) among the 7,530 unvaccinated women in the same study. The cumulative incidence rate among vaccinees was 1.85 percent, compared to 3.90 percent among unvaccinated women, representing a difference of 2.05 percentage points. Hospitalization rates associated with COVID-19 were 0.2 percent in women who had been vaccinated and 0.3 percent in women who had not been immunised.
“In this large population-based cohort of pregnant women, BNT162b2 immunisation was linked with a considerably lower risk of SARS-CoV-2 infection when compared with no vaccination, despite the fact that the absolute risk difference was minor,” the study’s authors concluded.
88 of the 105 infected and vaccinated women (83.8 percent) experienced coronavirus symptoms, compared to 149 of 179 (83.2 percent) of the uninfected women, a nonsignificant difference in the prevalence of coronavirus symptoms.
At 28 days, 4,788 of 7,530 women (63.6 percent) in each group were still alive and available for follow-up. The absolute cumulative number of occurrences in vaccinated women was 109, compared to 158 in unvaccinated women, with a difference in cumulative incidence of 0.80 percent between the two groups. The cumulative incidence rate in the vaccinated group was 1.55 percent, while it was 2.34 percent in the unvaccinated group.
10 women who had received the coronavirus vaccine and 46 women who had not received the vaccine tested positive for the virus during the 28-70-day follow-up period (hazard ratio [HR]: 0.33 per cent vs 1.64 per cent, respectively), representing an absolute difference of 1.31 percent and an adjusted hazard ratio (aHR) of 0.22.
In accordance with a time-varying covariate, the risk decrease increased over time following immunisation. There was no statistically significant difference between the aHRs (0.96) in the two groups of women in the 10 days following vaccination. A statistically significant reduction in the risk of death occurred among vaccinees from 11 to 27 days following vaccination, however (aHR, 0.46).
During the study’s follow-up period, 18.4 percent of the vaccinated group and 18.9 percent of the unvaccinated group reached the conclusion of their pregnancies respectively. When it came to preeclampsia (maternal high blood pressure and organ damage), smaller-than-expected babies for gestational age and birth weight, abortion, stillbirth, maternal mortality, or pulmonary embolism, there were no statistically significant differences between the two groups (blockage of a pulmonary artery).
No severe adverse events
Despite the fact that 68 patients reported vaccine-related adverse effects, none of them were considered severe. The most frequently reported side effects were headache (10 [0.1 percent]), weakness (8 [0.1 percent ]), nonspecific pain (6 [less than 0.1 percent ]), and stomach ache (less than 0.1 percent ). (5 [less than 0.1 percent ]). All symptoms subsided after a single day.
Women who had received vaccinations were 46 percent more likely than those who had not received vaccinations to be in their second or third trimester, compared to only 33 percent of those who had not received vaccinations. The median follow-up for SARS-CoV-2 infection was 37 days, with a mean age of 31.1 years and a mean follow-up of 31.1 years.
According to the scientists, changes in hormone levels and immunological function during pregnancy may increase the risk of contracting a viral infection. Furthermore, whereas COVID-19 infection in pregnancy is usually asymptomatic or moderate, it might result in hospitalisation to an intensive care unit and mechanical breathing, particularly during the third trimester of the pregnancy. Further research has linked symptoms of infection to increased likelihood of preterm birth and foetal distress during labour.
According to the researchers, the study was particularly important since, while a phase 3 clinical trial of the Pfizer vaccine demonstrated 85 percent efficiency in avoiding infection 7 days or longer after the second dose, pregnant women were not included in the study.