Introduction

Covid-19 is an infectious disease caused by the SARS-CoV-2 virus, which has resulted in the death of over 3 million around the world. Human corona viruses that were evident in the 1960s are responsible for upper respiratory tract infections. The virus was scavenged from the tracheal organ cultures from the respiratory tract of an adult with common cold.1 These viruses are single stranded RNA viruses with 5’cap and 3’poly (A) tail encompassing it. Virion diameters varying from 60 to 140nm and distinct spikes of 9 to 12 nm were clearly visible from the electron microscopy of the virus. The four structural proteins present in the coronaviruses are Spike (S), Membrane (M), Envelope (E) and Nucleocapsid (N).2

Due to the commencement of Covid-19 epidemic, attempts have been made to establish acquired immunity against Covid-19. Before the manufacture and authorization of covid-19 vaccines, there was a clear comprehension about the composition and function of corona viruses which pushed to the development of vaccines.3 Covishield, Covaxin and Sputnik V are the three vaccines available in India.4 Serum institute of India authorized the exigency use of Covaxin and Covishield in 16th of January 2021. Covishield is comprised of a recombinant and non-replicating chimpanzee adenovirus vector concealing the SARS-CoV-2 S protein.5 Covishield vaccination has two doses of 0.5ml each. The second dose is to be taken in between 4 to 12 weeks. The storage condition of Covishield vaccine is 2-8 degree Celsius for 6 months. This vaccine was produced by AztraZeneca. The efficacy of covishield was determined to be 80% after complete vaccination based on a case control study conducted in India. The covishield vaccine produced an increase in spike specific antibodies by day 28.6, 7

The SARS-CoV-2 antibodies which is produced from the inactivated COVID-19 vaccine in a mother before pregnancy can be passed on to the new born through the placenta.8 Umbilical cord blood is the medium which helps in the transfer of antibodies from a mother to her fetus.9 IgG is the only antibody class that significantly cross the human placenta. It is evident that the immune protection from a mother to unborn child will occur when the specific antibodies that are produced by either vaccination or infection are transferred through the umbilical cord blood.10 The visualisation of antibodies produced in cord blood sample can be done by using various methods. CLIA is an immunoassay technique which is used for the same. An antigen-antibody or an immune complex is formed through the binding of paratope and epitope of antibody and antigen respectively in the presence of complimentary particles. Immune complex is estimated by using labelled antibodies are the basis of CLIA.11

We studied cord blood for the presence of IgG obtained from vaccination of Covishield and about the side effects. The information brought forward from this study can be utilized to make sure that vaccines are effective for producing antibodies in mother which will be transferred to her baby through the cord blood.

Materials and Methods

The investigation was performed in the department of gynecology in a tertiary care hospital in Kerala, India between November 2022 and April 2023. The sample size was 40 (purposive sampling). During the time of delivery, umbilical cord blood was routinely collected as per the inclusion criteria, i.e. the pregnant women those who had completed two doses of Covishield vaccine. Pregnant women who were at risk in pregnancy (Latent pregnancy, Preterm delivery, Thyroid dysfunction, Gestational diabetes, Preeclampsia) and those who were not interested to participate in the study were excluded. The sample was collected from the study subjects after obtaining the informed consent and the collected cord blood was tested in the laboratory for identification of IgG antibodies using CLIA method. The result was obtained within 2 hours.

The primary outcome was the presence of IgG antibodies in the cord blood and the secondary outcome was to identify the side effects occurred during their vaccination. Demographic details, vaccination details and maternity details were collected by interviewing the subjects and details of any side effects experienced were also collected.

The cord blood collected was analyzed by using Electrochemiluminescence immunoassay. The main upper hands of this immunoassay are high specificity reduced number of reagents and also its incubation time. In this, a small amount of the subject’s sample is mixed with biotinylated and ruthenylated RBD antigen. This creates immune complexes when corresponding antibodies are present. Then, micro particles coated with streptavidin are added, which attach to the complex. The mixture is transferred to a measuring cell, where the particles are captured by an electrode and any unbound substance is removed. By applying voltage, electrochemiluminescence is induced and measured with a photomultiplier. The signal increases as the antibody titer value go up.

The data obtained from the study were statistically analyzed with the help of the software SPSS (version 22.0).

Results and Discussion

The samples were collected from 40 subjects. The mean age of the study group was 28 years (Table 1) and standard deviation was 4. The minimum age was reported as 19 years and maximum age was 39 years.(Figure 1) Majority of the subjects had completed their vaccination with in the interval of 3 months. All the 40 samples showed antibody production.(Figure 2) Here the antibody titer value was above 17.8 BAU/mL with a cut off value of 200 BAU/mL. It was evident that all the 40 samples had the presence of IgG antibodies.(Table 2) The association between the amount of antibody and interval between the doses were assessed by a statistical test called Chi-square test and it was found that there was no statistical association between these two variables. The Chi-square value was 0.81 and the P value was 0.368.

The details of occurrence of side effects due to vaccination were obtained from the subjects (Table 3) and it showed that 75% of the subjects had no side effects while the remaining 25% experienced minor side effects like fever, headache, fatigue and chills.(Figure 3)

The study aimed to find out if there are antibodies in the cord blood of individuals who received two doses of Covishield. With the emergency use authorization (EUA) of the three mRNA COVID-19 vaccines by the FDA, there has been a significant demand for research on their effectiveness and safety in pregnant and neonatal populations. The main findings of the study was, there were positive results for anti-spike antibodies in all the 40 samples; even though positive, 3 of the 40 samples showed antibody production less than 200 BAU/mL and those 3 subjects had completed their vaccination within one month duration; which is close to the studies done by Amikam U et al,12 and Flannery D et al.13

According to the study by Amikam U et al., they discovered that there is a connection between the antibodies against SARS-CoV-2 in the blood of both mothers and newborns when the mothers are vaccinated against COVID-19 during pregnancy. The study by Flannery D et al revealed that the levels of IgG in cord blood were positively related to the levels in maternal blood.

We observed that only 25% of the subjects have experienced minor side effects like fever and fatigue, while the remaining 75% had no side effects during their vaccination. This correlates with the studies done by Kamal D et al,14 and Pokharel K et al.15

The prospective observational study carried out by Kamal D et al observed the adverse events following Covishield vaccine amongst health care workers and they concluded that the vaccine is safe, well tolerated, and has a lower chance of causing reactions. Another descriptive cross-sectional study conducted by Pokharel K et al. proved that the Covishield vaccine has a good safety profile.

Figure 1

Age wise distribution

Figure 2

Detection of antibody

Figure 3

Distribution of status of side effects

Through our study, we have evaluated the transfer of antibodies from mother to child in those who have completed two doses of Covishield vaccine. The above mentioned studies can be correlated with our studies for understanding the maternal antibody transfer through the cord blood to the infant. Also, it is evident from our study that the Covishield vaccine is one with good safety profile. Once vaccines are readily accessible, determining the best time for maternal vaccination during pregnancy will involve considering both maternal and fetal factors, as well as ensuring sufficient time for neonatal protection.

Conclusion

The COVID-19 epidemic has been going on for over 3 years and has spread all around the world. Vaccines were made available to the public after clinical trials, but there is still limited knowledge about their effectiveness. Our study aims to examine the development of antibodies in cord blood after complete vaccination. Maternal immunization not only protects the mother and fetus from SARS-CoV-2 infection but also provides passive protection for the baby after birth through placental protection.

Our findings show that maternally derived antibodies have the potential to protect newborns from SARS-CoV-2 infection. We observed that all cord blood samples had high levels of anti-S antibodies following mRNA COVID-19 vaccination. Therefore, considering the ongoing pandemic since December 2019, it is recommended to consider vaccination for everyone worldwide, based on results from future large prospective studies.

Consent

As per international standard, informed consent was obtained from the participants and kept it on record by the author(s).

Ethical Approval

The study received approval and certification from the Institutional Research Committee (ECPS/RC-163/2023) of Ezhuthachan College of Pharmaceutical Sciences, Neyyattinkara, Trivandrum.

Source of Funding

None.

Conflict of Interest

The author has no conflict of interest to declare.