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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) still poses a serious threat to public health, especially due to the continuous emergence of SARS-CoV-2 variants with particular clinical relevance. Vaccines are considered the most promising strategy for curbing the pandemic. By the end of 2020, several vaccines had become available. Two SARS-CoV-2 mRNA vaccines are registered in Switzerland: Comirnaty® (Pfizer / BioNTech, licensed ≥12 y) and COVID-19 Vaccine Moderna® (licensed ≥18 y). Since early January 2021, the Epidemiology, Biostatistics and Prevention Institute at the University of Zurich serves as the reference vaccine center for the Canton of Zurich and study site of Corona Immunitas with the Zurich SARS-CoV-2 Cohort (ZSAC) and Zurich SARS-CoV-2 Vaccine Cohort (ZVAC) studies. Pregnant and lactating mothers were not included in the initial development and clinical evaluation of COVID-19 vaccines. The FOPH put no restrictions for lactating women on receiving the vaccine. Babies under the age of one year might be at higher risk of severe illness with COVID-19 than older children. This is likely due to their immature immune systems and smaller airways, which make them more likely to develop breathing issues with respiratory virus infections. Infants are currently (02 November 2021) not eligible for vaccination. The first clinical trial studying the Pfizer and BioNTech vaccine in babies aged 6 months started in March 2021.
There is little biological plausibility that the mRNA vaccine will cause harm in infants of breastfeeding women. Testing of the milk of mothers who received either the Pfizer-BioNTech or Moderna vaccine found no mRNA in their milk. The tiny amount of polyethylene glycol-2000 in Pfizer-BioNTech vaccine is not absorbed orally, so breastmilk PEG exposure from maternal immunization is not a concern. Neither of the currently available mRNA vaccines contains a preservative or adjuvant. While there is little plausible risk for the child, there is a biologically plausible benefit. Antibodies stimulated by the vaccine transfer into milk and may protect the breastfeeding child from infection with SARS-CoV-2.
Several studies demonstrated that SARS-CoV-2 specific IgA and IgG antibodies with binding and neutralizing capacity appear in breast milk soon after the first vaccination, with peak levels about 2 weeks after the second vaccine dose. The increase in IgG was higher than the increase in IgA. Breast milk IgG antibodies were synchronized with maternal serum IgG antibodies, and maternal serum antibody titers were equivalent to those of non-breastfeeding women and higher than those of women who previously had COVID-19. Around 7.1% of mothers reported an adverse effect in their breastfed infant, most frequently increased sleepiness and increased fussiness. No serious adverse reaction was reported in infants. A small percentage of women reported a temporary decrease in milk supply after mRNA vaccination or discoloration of milk.
It is essential to study the immunity of lactating women after vaccination, since it is currently unknown whether the antibodies excreted into the breast milk lead to immunization of the child and whether breast milk antibodies also provide protection against novel coronavirus variants. Primary research questions that are currently of high importance are concerned with the neutralizing capacity of vaccine-induced breast milk antibodies against novel variants of concern, the role of IgG in breast milk-transferred immunity, the presence of secretory IgA (sIgA) antibodies in breast milk after vaccination, and the extent of clinical protection from COVID-19 in breastfed infants of vaccinated mothers. Furthermore, T-cell responses specific to the coronavirus and their association with humoral Immune responses, as well as potential differences in T-cell responses between lactating and non-lactating women remain unstudied.
The objectives of our study are the following:
Primary objective:
Additional objectives:
Project lead: Jasmin Hiestand
Funding: Multiple donors
The SARS-CoV-2 pandemic has had a substantial impact on public health, economies and societies worldwide. From the early days of the pandemic, it was clear that joint research efforts of various disciplines would be necessary to tackle challenges posed by the virus and support policy and decision-making in Switzerland and worldwide. To this end, cohort studies emerged as valuable tools to assess the health, social and economic consequences of the pandemic.
The Zurich SARS-CoV-2 Cohort study was conceived in mid 2020 and set out to gather critical data to inform public health measures aiming to mitigate the spread of SARS-CoV-2 and to limit its impact on those affected. The study was established in close collaboration with the Department of Health of the Canton of Zurich, Switzerland, and brings together the expertise of epidemiologists, immunologists, and infectious disease specialists to answer questions on various aspects of SARS-CoV-2 in order to better understand its epidemiology and long term effects. It is an ongoing, population-based, longitudinal cohort of randomly selected individuals infected with SARS-CoV-2, including a complementary case-ascertained study of their close contacts in the Canton of Zurich. Comprehensive assessments regarding the longer-term health and medical consequences (i.e., Long Covid or post COVID-19 condition), re-infections, breakthrough infections following vaccination, as well as humoral and cellular immune responses, are conducted regularly up to three years after SARS-CoV-2 diagnosis.
Among others, the study has the following three main objectives:
For further information, please contact the study team via e-mail: zhcorona-cohort AT ebpi.uzh.ch.
Corona Immunitas
https://twitter.com/CoronaImmunitas
Project lead: Milo Puhan
Funding: Health Department Canton Zurich, UZH Foundation
