The impact of vaccination

Pandemics happen in waves. During the last century, this was the case with the Spanish flu. The first wave of the COVID-19 pandemic in India was managed through lockdowns and improvements in medical infrastructure for diagnosis and treatment. Now there is a vicious second wave of infections. This is related to the easing of lockdown restrictions and a large number of people who have remained uninfected until now returning to their normal lifestyle. In addition, mutant strains of the virus are contributing to the spread. This has impacted a large number of States including Tamil Nadu.

As in the case of any infectious disease, vaccination is the only way to reduce infection and control this pandemic. That effective vaccines became available within a year since the beginning of the pandemic is an incredible achievement. In India, too, vaccination against the virus is being offered. Vaccination with either Covishield or Covaxin was available from January 16 of this year. Initially, these vaccines were offered to front-line staff including doctors, nurses, technicians and hospital staff. From March 1, people over 60 years of age and also those over 45 years with co-morbidities became eligible for vaccination. Further, vaccination was expanded to cover all those above 45 years from April 1, 2021 and all those above 18 years from May 1.

A positive effect

In large trials, administration of Covishield reduced significantly the number of people who were infected compared to control. However, not everyone is convinced of the efficacy or necessity of the available vaccines. There are many reasons for this reluctance to get vaccinated. At a public health level, the negative side effects of vaccinating 100 million Indians remain low compared to the overall benefits of vaccination. Analysis of the available data from November 2020 and the second wave in Tamil Nadu suggest that the vaccination of people over 60 years of age has already started showing a positive effect.

The proportion of new COVID-19 positive patients in this age group has fallen since vaccination started. In comparison, the number of positive cases among those in the age group below 60 years shows an increase. This is illustrated in the accompanying graphs for Tamil Nadu and Chennai. The first graph shows the data for daily infections for the whole of Tamil Nadu according to each age group and the second shows the number of active patients for Chennai (according to available data). The Y axis on the left shows the proportion of daily infections or active cases while that on the right shows the numbers vaccinated.

The impact of vaccination

Numbers that bode well

An analysis of the absolute numbers shows an increase in cases across all age groups. However, the percentage of infected people over 60 years of age shows a definite decrease. At present, in Tamil Nadu only 16% of those above 60 years and 4% of those below 60 years (projected population in 2021) have been vaccinated (one dose). However, there is a 7% decrease ininfections among those above 60 years of age. These results strongly suggest the positive impact of vaccination. Similar reduction can be expected in the number of deaths among those above 60 years of age. However, analysis of death data is not meaningful at this stage owing to large scatter in reported deaths.

This bodes well for the future. Increasing the population which can be vaccinated is a definitive way to control the pandemic. The government has now allowed vaccination of all people above 18 years, a good step forward. However, educating the public about the benefits of vaccination and explaining that major side effects are rare will be important to ensure acceptance. Vaccinating a large number of people will take time and effort but is necessary to prevent further waves of infection and the possible emergence of new mutant strains. While the vaccination programme will help in reducing the effects of the second wave, the only way to contain it quickly is an increased adherence to COVID-19-appropriate behaviour.

T.S. Ganesan is Professor, Medical Oncology and Clinical Research, Cancer Institute (WIA), Chennai; R. Rajaraman is Professor, Homi Bhabha National Institute, Indira Gandhi Centre for Atomic Research, Kalpakkam; and Dr. R. Shankar is Honorary Professor, The Institute of Mathematical Sciences, Chennai

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Printable version | Jun 18, 2021 8:51:22 AM |

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