INDIA’S PRAGMATIC VACCINATION STRATEGY AGAINST COVID-19: A MATHEMATICAL
MODELLING BASED ANALYSIS
Authors: Mandal Sandip , Arinaminpathy Nimalan , Bhargava Balram , Panda Samiran 
Published: May 2021

Abstract

Objectives
To investigate the impact of targeted vaccination strategies on
morbidity and mortality due to COVID-19, as well as on the incidence of
SARS-CoV-2, in India.

Design
Mathematical modelling.

Settings
Indian epidemic of COVID-19 and vulnerable population.

Data sources
Country specific and age-segregated pattern of social contact, case
fatality rate and demographic data obtained from peer-reviewed literature
and public domain.

Model
An age-structured dynamical model describing SARS-CoV-2 transmission in
India incorporating uncertainty in natural history parameters was
constructed.

Interventions
Comparison of different vaccine strategies by targeting priority groups
such as key workers including health care professionals, individuals with
comorbidities (24 – 60 year), and all above 60.

Main outcome measures
Incidence reduction and averted deaths in different scenarios, assuming
that the current restrictions are fully lifted as vaccination is
implemented.

Results
The priority groups together account for about 18% of India’s
population. An infection preventing vaccine with 60% efficacy covering all
these groups would reduce peak symptomatic incidence by 20.6% (95%
uncertainty intervals (CrI) 16.7 - 25.4), and cumulative mortality by 29.7%
(95% CrI 25.8-33.8). A similar vaccine with ability to prevent symptoms (but
not infection) will reduce peak incidence of symptomatic cases by 10.4% (95%
CrI 8.4 – 13.0), and cumulative mortality by 32.9% (95% CrI 28.6 - 37.3). In
the event of insufficient vaccine supply to cover all priority groups, model
projections suggest that after keyworkers, vaccine strategy should
prioritise all who are > 60, and subsequently individuals with
comorbidities. In settings with weakest transmission, such as
sparsely-populated rural areas, those with comorbidities should be
prioritised after keyworkers.

Conclusions
An appropriately targeted vaccination strategy would witness substantial
mitigation of impact of COVID-19 in a country like India with wide
heterogenity. ‘Smart vaccination’, based on public health considerations,
rather than mass vaccination, appears prudent.

Strengths and limitation of this
study

The model in this study is informed by age-dependent risk
factors for SARS-CoV-2 infection among contacts, and is
stratified by co-morbidities (diabetes and/or hypertension), and
vaccination status.

Data on mortality and large-scale contact tracing from
within India, and the recent national sero-survey results were
used, which constituted a major strength of this
investigation.

Distinguishing between ‘infection’ and ‘symptomatic disease
‘ preventing vaccines, the model was simulated under a range of
scenarios for the basic reproduction number (R0).

Should they have been available, real life country-specific
data on excess risks of deaths due to comorbidities would have
added strength to the presented model.

Key priority group-specific data on social mixing and
potential associated transmission was not available, and
remained as a limitation.