COVID 19 was identified in January 2020 as the cause of a pneumonia epidemic in China . It was declared a pandemic by the World Health Organization (WHO) due to the high contagion rate . As of August 28, 2020, COVID-19 has caused the death of 833,135 (3.40%) people worldwide and infected 24,532,835 . This pandemic has prompted the world to implement drastic prevention methods based on barrier measures, isolation, quarantine and restriction of population movements . These measures had a considerable negative impact on the economy and on public health policies such as vaccination . In Senegal, the Expanded Programme on Immunization or EPI (Table 1) was launched in 1974 with vaccination coverage that has led to the eradication of several childhood diseases and a reduction in mortality among children under 5 years of age . The objective of this work was to evaluate the impact of the COVID-19 and preventive measures on routine hospital immunization since the advent of this pandemic in the country on 2 March 2020.
This is a retrospective cross-sectional study carried out during the month of August 2020 in the vaccination unit of the ABASS NDAO hospital center (CHAN) in Dakar, which is a level III public hospital. The vaccination unit is very busy because CHAN is home to one of the largest mother-child center in the country with a maternity unit that receives an average of 5000 parturients per year. All newborns born in the facility are directly referred to the vaccination unit and are followed according to the vaccination calendar until the age of 15 months. The unit also receives children born outside the facility. We compared the data from the vaccination unit for the period of March to August for the last three years (2018, 2019 and 2020). The parameter studied was the number of vaccine doses administered for the different periods according to the EPI: at
Table 1. Calendar of the expanded program on immunization (EPI) in Senegal.
BCG = Bacillus Calmet Guerrin, OPV = oral polio vaccine, IPV = injectable polio vaccine, FJ = yellow fever, MR = measles-rubella, Pentavalent = Diphtheria + Tetanus + Whooping cough + Hepatitis B + Hib infections.
birth (BCG, poliomyelitis), at 6 weeks then at 10 weeks (pentavalent, pneumococcal, rotavirus and polio vaccine), at 14 weeks and at 9 months (measles, rubella and yellow fever). The data were collected from the vaccination register and collected on a pre-established survey form. Data analysis was done with version 9.4 of the SAS software.
For vaccines administered at birth (tuberculosis, oral polio), the number of doses administered at the vaccination unit level was 80 for March 2018, 32 for March 2019 and 40 for March 2020. The same trends are observed when comparing the months of April, May, June, July and August of the year 2020 with the last two years (2018, 2019). The number of doses administered for birth vaccines by month and year are shown in Figure 1. For vaccines administered at week 6 according to the EPI, there are 36 doses administered in March 2018, 41 doses in 2019 and 30 doses in 2020. In April, the number of doses was 36 in 2018, 29 in 2019 and 15 in 2020, a decrease of 50% compared to March. In July the number of doses administered was 40 in 2018, 35 in 2019 and 15 in 2020, a reduction of 37% compared to 2018 and 42% compared to 2019. The numbers of doses administered for the sixth, tenth and fourteenth week vaccines are shown in Figures 2-4. For yellow fever, measles and rubella vaccines administered at month 9, the number of doses administered was 10 in 2018, 24 in 2019 and 20 in 2020. In April, the number of doses administered in 2020 fell to 5 compared to 5 in 2020, a drop of 20.8% compared to March. The numbers of doses administered for the ninth month vaccines by month and year are shown in Figure 5.
In Senegal, the first case of COVID 19 was declared on 2 March 2020 and a few weeks after the state of emergency was declared in the country, limiting the mobility of the population. The number of doses administered for tuberculosis and polio vaccines at birth in March 2020 was not impacted by VIDC 19. This could be explained by the fact that the pandemic had no impact on births during this
Figure 1. Number of doses administered for vaccines at birth against tuberculosis (BCG) and oral poliomyelitis according to the month from 2018 to 2020.
Figure 2. Number of doses administered for the vaccines of the sixth week according to the month from 2018 to 2020.
Figure 3. Number of doses administered for the tenth week vaccines according to the month from 2018 to 2020.
Figure 4. Number of doses administered for the 14th week vaccines according to the month from 2018 to 2020.
Figure 5. Number of doses administered for the ninth month vaccines according to the month from 2018 to 2020.
period and that isolation measures were still limited at the individual level. There was a marked decrease in the number of doses administered for the sixth, tenth and fourteenth week vaccines during the period April to August 2020. Similar results were observed in developed countries   . This period corresponds to a steady increase in the number of cases reached and coincides with the implementation of physical distancing measures such as curfews, closure of steps and places of worship, and reduction in the number of passengers on public transport . This impact could also be explained by the fact that the message about staying at home initially overwhelmed the message that the vaccination programme should continue to function as usual and also led to disruptions at the vaccination units . The disruption of immunization services could trigger secondary outbreaks of vaccine-preventable diseases and also exacerbate the longstanding inequality in immunization coverage, especially in urban areas .
COVID 19 has certainly impacted the routine vaccination of children. Measures to combat this pandemic should not make us forget routine vaccination, especially in our resource-limited countries. It is essential to continue these vaccination programmes for children under 5 years of age and to identify children who have missed vaccine doses for catch-up. This could prevent the reappearance of new epidemics such as measles, which could be associated with high morbidity and mortality.
- Amadou Sow, Modou Gueye, Djibril Boiro: Design, data collection and writing.
- Idrissa Demba Ba, Abou Ba, Aliou Thiongane, Papa Moctar Faye: Reading, correction.
- Amadou Lamine Fall, Assane Sylla, Ousmane Ndiaye: Validation.
We would like to thank the staff of the vaccination unit, in particular Mrs. Fall Awa Touré and the management of the ABASS NDAO hospital center in Dakar.
 Pascarella, G., Strumia, A., Piliego, C., Bruno, F., Del Buono, R., Costa, F., Scarlata, S. and Agro, F.E. (2020) COVID-19 Diagnosis and Management: A Comprehensive Review. Journal of Internal Medicine, 288, 192-206.
 Di Gennaro, F., Pizzol, D., Marotta, C., Antunes, M., Racalbuto, V., Veronese, N. and Smith, L. (2020) Coronavirus Diseases (COVID-19) Current Status and Future Perspectives: A Narrative Review. International Journal of Environmental Research and Public Health, 17, 2690.
 Staff of the Times of Israel (2020) Vaccinations Drop amid Fears of VIDOC-19, Raising the Spectre of a New Measles Epidemic. Times of Israel.
 Hart, C. (2020) Confessions of a Consultant IN Paediatric Practice Management. The Effect of Covid-19 on Vaccination Rates.
 Santoli, J.M., Lindley, M.C., DeSilva, M.B., Kharbanda, E.O., Daley, M.F., Galloway, L., et al. (2020) Effects of the COVID-19 Pandemic on Vaccine Ordering and Administration Routine Paediatrics—United States, 2020. Morbidity and Mortality Weekly Report (MMWR), 69, 591-593.
 Chandir, S., Siddiqi, D., Setayesh, H. and Khan, A.J. (2020) Impact of COVID-19 Lockdown on Routine Immunisation in Karachi, Pakistan. The Lancet Global Health, 8, E1118-E1120.