An Estimate of Protective Immunity against SARS-CoV2: Comparison of Different Vaccine Types

: Several types of vaccines have been approved to prevent SARS-CoV-2 infection. Few studies are conducted on the efficacy of COVID-19 vaccines. Vaccination is important to eliminate and fight SARS-CoV-2 infection and several vaccines have been approved. This study aimed to assess the incidence density of COVID-19 infection among the community, estimate the effectiveness of different types of vaccines (inactivated virus, viral vector or mRNA) and efficiency of incomplete and complete vaccination. In this observational cross-sectional study, a total of 4924 specimens were received from 1 st January 2022 to 2 nd February 2022 for the detection of SARS-CoV-2. The patient’s age, gender, and vaccination data were recorded and S, N, and ORF 1ab genes were amplified after RNA extraction through PCR. out of which 1034 (20.99 %) cases were positive. Among 1034 (20.99 %) positive cases, 418 and 616 patients were vaccinated and non-vaccinated respectively. The cases of SARS-CoV-2 in vaccinated patients were categorized into a sudden infection (≤ 10 days) and late infection (≥10 days) after the incomplete and complete dose of vaccination. Vaccination provides partial protection against SARS-CoV-2 infection. This might be due to the low efficacy and inability to detect recent variations in the protein structure of the virus.


INTRODUCTION
Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); an emerging infectious disease was first reported at the end of 2019 in Wuhan.Globally SARS-CoV-2 infection has occurred in almost every country with millions infected and hundreds of thousands dead [1].The treatment and prevention of an infection depend on effective drugs and vaccines.In addition to traditional inactivated vaccines, new technologies are being employed to develop COVID-19 vaccines, such as mRNA/ DNA vaccines, genetically engineered vaccines, and vaccines based on adenovirus-based vectors [2].For COVID-19, mRNA-based vaccines have shown the highest levels of protection, followed by viral vectors, protein subunits, and wholeinactivated viruses [3].
To eliminate and fight SARS CoV-2 infection, vaccination is important and several COVID-19 vaccines have been approved, including BBIBP-CorV (Sinopharm, China) and CoronaVac (Sinovac Biotech, China) an inactivated virus vaccine with aluminum hydroxide adjuvant of 2 doses are given [4].CanSino Bio Vaccine/ Ad5-nCoV (China), Gam-COVID-Vac/Sputnik V (Gamaleya National Research Center for Epidemiology and Microbiology, Russia) and ChAd0x1 (AZS1222) (AstraZeneca/ Oxford UK) are viral vector vaccines.mRNA-1273 (Moderna US) and BNT162b2 (Pfizer-BioNTech US) are mRNA vaccines [5,6].This study was conducted to determine the effectiveness of different types of vaccines against COVID-19 and the chances of infection in partially and fully vaccinated individuals.

Study Design
This observational cross-sectional study was carried out 1 st January, 2022 to 2 nd February, 2022 at the Department of Pathology, Mardan Medical Complex (MMC).The study population included patients of both genders, age above 20 years, suspected COVID-19 patients (vaccinated and nonvaccinated), Ct values of N, S and ORF1ab genes and those who visited MMC Mardan.Patients having age less than 20 years, asymptomatic, coinfected, or other respiratory disease were excluded from this study.

Ethical Statement
Ethical approval was obtained from the ethical committee of the hospital, Mardan Medical Complex (MMC) for this study.

Sample Size
A total of n=1034 COVID-19 positive patients were included in the current study.The patient information such as age, gender, and history of vaccination including vaccine type and vaccination dose (incomplete or complete dose) was recorded through a questionnaire form.COVID-19 positive patients were categorized into 2 groups; sudden infection (≤10 days) and late infection (≥10 days) after the incomplete and complete dose of vaccination.

Sample Processing
SARS CoV-2 RNA was extracted through an auto extractor (Hangzhou Bigfish Biotech Co Ltd, China) and Real-Time Polymerase Chain Reaction (RT-PCR) was performed for amplification of S, N and ORF 1ab genes (Rotor-Gene, Qiagen, Germany).The cycle threshold (Ct) values of the study patients were categorized as high (Ct 28-34.9)and low (18-27.9).The Ct values were compared between the patients with severe disease and mild disease.

Statistical Analysis
Quantitative variables such as mean, standard deviation, categorical variables (frequency and percentages) and significance among variables were calculated through SPSS Version 22.0.

Study Population and Characteristics
A total of 4942 specimens of the suspected COVID-19 patients were screened for the detection of SARS-CoV-2.The SARS CoV-2 was detected in 1034 (20.99 %) specimens of the suspected patients through RT-PCR.The demographic data of all the COVID-19 positive patients is tabularized in Table 1.Significant (p value <0.0001) was observed for vaccinated and non-vaccinated patients.The infection rate was significantly high in females than in males, while a non-significant difference was observed between the different age groups (Table 1).vaccinatedpatients.Incomplete and complete vaccination dose among the vaccinated patients and COVID-19 within ≤ 10 days and after ≥ 10 days of vaccination among incomplete and complete vaccinated patients are shown in Table 2.

N, S and ORF1ab Gene Amplification in COVID-19 Patients
This observational cross-sectional study was carried out from 15 November 2021 to 15 January 2022).We screened a total of 4924 specimens of the suspected COVID-19 patients for detection of SARS-CoV-2, with the incidence of positive samples n= 1034 (21.6 %) patients, out of which n=667 (64.50 %) were males and n=367 (35.49%) were females.The COVID-19 patients were categorized in three groups according to age: group 1 (21-40 years), group 2 (41-60 years), and group 3 (60 and above).Each group comprised of 126 (30.14 %), 150 (35.88 %) and 142 (33.97 %) patients respectively.The highest number of positive patients were observed in group 2 followed by groups 3 and group 1.The mean age for each group was 30 years, 50.17 years, 75.18 years for group 1, group 2, and group 3 respectively.For all the vaccinated patients the mean age was 52.58 years.A previous study reported that SARS CoV-2 infection was predominant in patients ranging age group 25-44 years followed by the age group higher than 45 years and less than 25 years [7].
None of the patients were infected with SARS CoV-2 after the incomplete and complete dose of Sputnik V vaccination within ≤ 10 days.All patients n=20 (100 %) and n=2 (100 %) were COVID-19 positive after ≥ 10 days of vaccination, similarly, none of the patients was COVID-19 positive after the incomplete and complete dose of Astrazeneca vaccination within ≤ 10 days.n=16 (100 %) and n=2 (100 %) had COVID-19 after the incomplete and complete dose of ChAd0x1 (AZS1222) vaccination after ≥ 10 days.Patients incomplete vaccinated with mRNA-1273 (n=4) and BNT162b2 (n=6) were COVID-19 positive after ≥ 10 days.Another study has reported COVID-19 vaccines to offer protection against SARS CoV-2 variants, including Delta, after completion of the vaccination series, and the effect of partial uptake of vaccines is found to be suboptimal [ 9,10].

CONCLUSION
Vaccination provides partial protection against SARS COV-2.This might be due to the low efficiency and potential to detect recent variations in the protein structure of the virus.Furthermore, incomplete vaccination in the community also increases the risk of COVID-19.The study also concluded that chances of SARS-CoV-2 infection (sudden and late) are high in patients vaccinated with inactivated vaccines (Sinopharm and Sinovac).To our knowledge, this is the first study to describe the effectiveness of different types of vaccines against COVID-19 and reported COVID-19 within ≥ 10 days or more ≤ 10 days among incomplete and complete vaccination doses.

LIMITATIONS
The limitations of this study were the lack of followup of all the vaccinated patients, study duration was short, lack of clinical correlation among the vaccinated patients and COVID-19 variants were not detected and Ct values among incomplete and complete vaccination in vaccinated patients were not calculated.

RECOMMENDATIONS
Vaccines needs to be updated periodically to increase clinical efficacy against SARS CoV-2 variants and detection of SARS CoV-2 infection and other complications at the time of vaccination is needed to overcome the efficiency and effectiveness of vaccine among COVID-19 patients.

CONFLICT OF INTEREST
The authors declared no conflict of interest.

Table 3
the rest 112 (18.18 %) had a high Ct value while out of 418 vaccinated patients, 105 (25.11 %) had low Ct value and 313 (74.88 %) had high Ct value (Table

Table 1 .
Demographic data of COVID -19 vaccinated and non-vaccinated patients