The Impact of COVID-19 Vaccine on Rate of Hospitalization and Outcome of COVID-19 Infection in a Single Center in the Eastern Province of Saudi Arabia

Background: Coronavirus 2019 (COVID-19) is an emerging and quickly disseminating disease that causes deleterious complications. Vaccines have the potential to improve population immunity and avoid serious disease and deaths. Methodology: A retrospective cohort study was conducted on 331 hospitalized patients with Covid 19 infections between April 2021 and July 2021 at King Fahad University Hospital. Data was collected from the medical records stored in the electronic health system of the hospital. Results: 27.7% of the participants required ICU admission, and 10.5% required mechanical ventilation. The mortality rate was around 7.23% of the infected cases. Two thirds of the study participants (64.05%) did not receive any vaccine, and it can be noted that only 16.8% had received 2 doses. The results suggest that the status of receiving a vaccine has signi�cantly in�uenced the length of hospital stay, decreasing it by 19.7%. In addition, the date of receiving the vaccine was statistically signi�cant in decreasing the incidence of ICU admission, as those who have received a vaccine for longer than 14 days needed ICU admission 82% less compared with their counterparts. The type of vaccine did not impact on any of the reported outcomes in the form of hospitalization rate, ICU admission and death. Conclusion: The majority of the study participants didn’t receive any vaccines before their admission with COVID 19, which in turn prolonged their hospital stay. This necessitates that the public require more awareness regarding the importance of receiving the vaccine.


Introduction
Coronavirus disease 2019 (COVID-19) is an emerging and quickly disseminating disease that causes various deleterious complications.It's caused by SARS-CoV-2, a member of the Coronavirus family.It was rst discovered in Wuhan, China, in November 2019, and the rst case was reported to the World Health Organization (WHO) on December 31st, 2019.[1] On March 11, 2020, the WHO labelled COVID-19 as a global pandemic.Despite the government efforts to reduce transmission, the number of cases continued to escalate rapidly, posing a public health compromise.[2] By June 25,2021, a total of 179,686,071 positive cases were registered worldwide, including 3,899,172 deaths.[2] As the pandemic progresses, it will have a signi cant in uence on mortality, particularly among those with pre-existing comorbidities.[3] Vaccines have the potential to improve the population's immunity and avoid serious disease and death.At the time of writing, six vaccines (P zer BioNTech -Conirnaty, Moderna -mRNA-1273, AstraZeneca -Vaxzevria, Janssen -Ad26.COV 2-S, Beijing CNBG -BBIBP-CorV, Sinovac -CoronaVac) have received WHO Emergency Use Listing -EUL, with e cacy in phase 3 studies reaching 95%.[2] Up to date 17,341,114 vaccine doses have been given in Saudi Arabia, 15,894,908 of them are rst doses, while 1,446,237 of them are second doses.[4] To quantify the e ciency of these vaccinations at the level of the population and in real-world settings in terms of reducing the rate of hospitalizations and deaths from COVID 19 infection, we need large post-licensure epidemiological studies to supplement the results of pre-licensure trials.[4]  Patients who were admitted to the hospital for another reason and had an incidental nding of a positive COVID 19 test.
After applying the exclusion criteria to 784 patients and eliminating duplicated cases.331 individuals were eligible for their data to be utilized in this study.
Data was collected from the medical records stored in the electronic health system at KFUH.A data collection form was utilized to segregate data into different sections.The form included ve sections.The rst section was concerned with demographic data, including the patient's sex, date of birth, age, and nationality.The second section included the patient's laboratory tests like Complete Blood Count (CBC), Renal Function Test (RFT), lactate dehydrogenase (LDH), in ammatory markers, and D-dimer.The third section was about COVID-19 Severity Data, including the severity of the infection, any complications such as Cytokine Storm, sepsis, Acute Respiratory Distress Syndrome (ARDS), and multi-organ failure.The fourth section was about the outcome of COVID-19 infection, such as hospital admission duration, any need for Intensive care unit (ICU) admission, or ventilation, and any related mortality.The nal section was about vaccination information such as the type of the vaccine, number of doses, and the date of the last dose.

Data analysis:
Data was transferred to an excel sheet and then analysed using the SPSS 26 version.
Descriptive statistics were performed on both variables, and average was reported for quantitative variables or frequency for qualitative variables.
Chi square for independent test was used to assess the association between categorical variables.
The level of statistical signi cance was set at (p < 0.05).

Results
A total of 331 participants were included in the study.(Table 1) presents the Socio-demographic characteristics of these patients.
The results showed that 70% of the study participants were aged between 41 and 80 years old.The least aged groups were those less than 20 years old, followed by those who were more than 80 years old.Furthermore, the majority of the study participants were males (58.91%) and (41.09%) were females.Regarding nationality, it can be noted that 62.84% of the study participants were Saudi citizens, whilst 37.16% of the respondents were non-Saudi.In terms of marital status, the majority of the participants were married (58.91%) compared to (39.58%) who were single.The least proportion were the widows constituting 1.51%.
The results of the complete blood count revealed that the percentage of abnormal WBC increased by 16% at the peak time compared to the admission.This was also associated with an increase in the WBC level from admission of 7.62 to the peak of 12.79.Moreover, 81.87% of the study participants showed a normal platelet count compared to 18.13% who had an abnormal level of platelets.Interestingly, two thirds of the study participants had normal levels of neutrophils, 63.85%, and this normal result was seen in the proportion of participants who had normal lymphocyte count 82.17%.This was also associated with normal neutrophil and lymphocyte levels of 1.24 and 1.94, respectively.(Table 2) summarizes the results of the complete blood count.
The results of renal function tests demonstrated that the majority of the study participants had normal blood urea nitrogen levels as 76.73% were allocated within the normal range with an average level of 7.62.It is noted that around half of the study participants had normal creatinine levels of 12.79.Regarding the electrolyte levels, the proportion of patients with normal sodium and potassium levels was identical with a percentage of 75.22% and an average level of 19.05 for sodium and 1.45 for potassium.Similarly, around 65% of the study participants had normal chloride levels with an average CO2 of 1.13, as reported in (Table 3).
The results of LDH showed that the majority of the study participants (83.98%) had abnormal levels with an average of 451.36.Also, this is associated with abnormal Erythrocyte Sedimentation Rate (ESR) as 79.75% had abnormal levels with an average level of 683.18.In terms of C-Reactive Protein (CRP), 67% of the study participants showed an abnormal range with an average of 53.41.This is also noted in the number of participants who have an abnormal D-dimer of 66.77%, with an average of 67.10.Likewise, ferritin was abnormal in 80.7% of the study participants, with levels of 12.30, as described in (Table 4).
The results obtained from the preliminary analysis of COVID 19 severity data suggested that 78.85% of the study participants had evidence of pneumonia in the chest x ray.Regarding the symptom severity criteria, 36.85% of the participants revealed oxygen saturation less than 93%, while 26% of patients showed lung in ltrates > 50% of the lung eld within 24-48 hours of admission.However.Only 6% of the recorded cases had a PaO2/FiO2 < 300.Similarly, the results of critical symptom surveillance revealed that 45.71 percent of participants were at high risk of developing cytokine storm due to abnormal ferritin > 600, LDH > 250, or D-dimer > 1, as shown in (Table 5).
It is apparent from this table that the average length of hospital stay is around 10.26 days.The results also highlighted that 27.71% of the study participants needed ICU admission and 10.54% required a mechanical ventilator.The mortality rate was around 7.23% of infected cases, as illustrated in (Table 6).
The ndings presented in (Table 7) revealed that two thirds (64.05%) of the study participants did not receive any vaccines.It can also be noted that only 16.8% of the vaccinated individuals received the second dose.P zer was the most frequent vaccine type given to the study participants in both the rst and second dose.Furthermore, 80% of the study participants received the vaccine more than 14 days before their admission.
The results of comparison between the vaccine information and the COVID 19 outcome suggest that the status of receiving a vaccine has signi cantly in uenced the length of hospital stay as the study participants who did not receive the vaccine reported longer hospital stay (CI 95%, P:0.02).Receiving the vaccine reduced the length of hospitalization by 19.7%.The date of receiving the vaccine was also statistically signi cant in relation to the incidence of required ICU admission, as those who have received a vaccine for longer than 14 days had fewer ICU admissions compared with their counterparts (CI 95%, P:0.03).The vaccine reduced the mortality rate by 50%, but it was not statistically signi cant (CI 95%, P:0.16).
The type of vaccine and number of doses did not impact on any of the reported outcomes in the form of need for ICU admission, mechanical ventilator, death, or length of stay as reported in (Table 8)

Discussion
In regards to the demographic factors, the majority of the study participants were males (58.91%), and (41.09%) were females.
Likewise, in an observational study of Covid-19 patients hospitalized in Bergamo, Italy, out of 431 adult patients admitted, males constituted the majority of the participants, with a percentage of 72.4%, whereas females constituted 27.6%.[5] In respect to age, the majority of the study participants were aged between 41 and 80 years old.This was consistent with a cohort done in metropolitan Atlanta and Georgia with 305 hospitalized COVID 19 patients where the median age was 60 years old with an interquartile range between 46-69 years old showing greater propensity for this age group.[6] In terms of marital status, the majority of the participants were married (58.91%) compared to 39.58% who were single and 1.5% were widows.In contrast, a cross-sectional study was done in Ecuador.It included 9486 participants and showed that in terms of civil status, 39.3% of the participants were single, 38% were married, 13% were cohabitants with their partners, 5.4% were divorced, and 1.3% were widows.[7] Patients infected with COVID-19 have variations in the symptoms, ranging from asymptomatic status to severe manifestations.Those with a mild type of the disease could have a fever, in addition to sore throat, cough, arthralgia, fatiguability, vomiting, and diarrhea.The severe form has a wide range of symptoms, including a respiratory rate of more than 30 breaths per minute, oxygen saturation of 93% in room air, PaO2/FiO2 of 300, and lung in ltrates in more than 50% of the lung eld.The critical type comprises acute respiratory distress syndrome (ARDS), sepsis, cytokine storm and multi-organ failure.[8] 78.8% of the study participants had evidence of pneumonia in their chest X-ray, 36.8% had o2 saturation less than 93% in room air, 10.7% had ARDS, 3.5% had sepsis, and 45.7% met the criteria for cytokine storm.In comparison, a meta-analysis of 21 studies with a total of 47,344 patients looking for symptoms and complications of COVID 19 discovered that ARDS risk was 9.4%, kidney injury was 2.1%, and shock was 4.7 %. [9] Another retrospective study was conducted in China to evaluate the severity of symptoms on admission, complications, and outcome in COVID 19 patients.548 patients were enrolled.The study identi ed that 49.1% of patients had severe presentations upon admission.Older age, underlying hypertension, high cytokine levels, and high LDH levels were signi cantly associated with severe COVID-19 on admission.According to the survival analysis, male sex, older age, leucocytosis, high LDH levels, and high-dose corticosteroid use were all associated with death in patients with severe COVID-19.[10] The severity and mortality rates of COVID 19 vary across different studies.In our study, 27.7% of the participants required ICU admission, 10.5% required mechanical ventilators, with a 7.2% mortality rate.According to a meta-analysis from 37 articles, about one-third of the patients infected with Covid 19 were admitted to the ICU with severe disease features, with mortality exceeding 30% of the total number of patients admitted.[11] Furthermore, it's speculated that the widespread availability of the vaccine to be associated with a decline in the number of cases admitted to the hospital and to the ICU.In accordance with that, our study displayed that taking the vaccine more than 14 days prior to hospitalization reduced ICU admissions by 82% and receiving a vaccine reduced hospital stay by 19.7%, which demonstrates that vaccines have a tangible in uence in decreasing the length of hospitalizations and ICU admissions.A prospective cohort study was done in 2021 in Scotland to explore the association between the widespread distribution of rst doses of COVID-19 vaccines and COVID-19 hospitalizations.A total of 1,331,993 individuals were vaccinated during the study duration.The average age of those who had been immunized was 65.The 1st dose of the P zer vaccine reduced COVID-19 admission to the hospital by 91% at 28 to 34 days after immunization.During the same period, the AstraZeneca vaccine reduced hospitalizations by 88%.When the study was limited to patients aged 80 and above, the combination of vaccine effects in reducing COVID 19 hospitalization was similar, reaching up to 83 percent at 2834 days post-vaccination.The widespread distribution of the 1st doses of both vaccines was linked to a signi cant decrease in the frequency of COVID-19-related hospitalization in Scotland, according to the forementioned ndings.[12] In 2021, A case-control study was conducted in England to determine the e cacy of the P zer (BNT162b2) vaccine and the AstraZeneca (ChAdOx1) vaccine against con rmed COVID-19 hospitalizations, and deaths in the real world.All individuals in England aged 70 and more were included in the study (over 7.5 million).cases who had received 1 dosage of P zer had a 43% lower chance of emergency hospitalization and a 51% lower risk of mortality.Cases who received 1 dose of AstraZeneca vaccine had a 37% lower probability of emergency hospitalization.Due to the vaccine's later introduction, there was insu cient follow-up to examine the AstraZeneca effect on mortality.When the effect against symptomatic illness was considered, one dose of either vaccines was around 80% effective to prevent hospitalization.According to the ndings, vaccination with any of the two options was linked to a considerable decrease in symptomatic COVID-19 positive cases in the elderly population with better protection against severe disease.[13]

Conclusion
According to the available literature, there were no studies conducted on the Saudi population to assess the e cacy of vaccination in reducing hospitalization and deaths from COVID-19.Therefore, it is very important to assess the vaccine e cacy in Saudi Arabia to bene t the population in increasing awareness and in reducing severe diseases and deaths.

Limitations And Recommendations
The limitations of our study include the small sample size of eligible patients, which can affect the generalizability of the results.In addition, the study included a speci c population of patients from one centre.We recommend multicentric studies in the future with patients from different regions in Saudi Arabia, including rural provisions where lack of immunization awareness may be present.

MethodologyA
retrospective cohort study of 784 hospitalized patients with Covid 19 infection at King Fahad University Hospital (KFUH) between April 2021 and July 2021 was conducted.Inclusion criteria: All adult patients admitted due to COVID-19 infection in KFUH with no prior history of COVID-19 infection regardless of their vaccination status.Exclusion criteria: Pregnant women and children < 18 years old.Patients who tested positive for COVID 19 prior to April 2021.

Table 1
Comparison Vaccine information in relation to the COVID-19 disease Outcome Data ARDS: Acute respiratory syndrome PaO2/FiO2: the ratio of arterial oxygen partial pressure (PaO2 in mmHg) to fractional inspired oxygen