april, 2019 | The Health
issue: Vaccine
100 percent effectiveness?
Vaccines may not be 100 percent effective. Different
people respond differently to vaccines, and it is pos-
sible that some people may not generate an adequate
immune response to the vaccine. As a result, these
individuals may not be effectively protected. There are
some vaccines that need additional doses to help raise
immunity against specific diseases. The protection
offered by vaccines is better than no protection at all.
Shouldn’t natural immunity be better
than vaccination?
In order to develop natural immunity for a specific
disease, a child needs to be infected by the bacteria or
virus causing it, and to completely recover from the
disease first. This however, puts the child at risk of
potentially life-threatening complications.
Vaccines on the other hand, puts killed or weakened
bacteria/virus causing the disease into the body in a
controlled manner, which in turn helps the body to
produce natural immunity against said disease. And
it is all done without putting your child through such
a big risk.
Vaccines uses a person’s natural response to
diseases to stimulate the immune system so that if
someone is exposed to the specific pathogen in the
future their immune system can ‘remember’ it and
mount an effective response to either stop the disease
from developing or reduce the severity of the disease.
How long does it last?
Different vaccines provide protection for varying
amounts of time. This is a result of the different ways
vaccines are made. Certain vaccines may confer life-
long immunity. Other vaccines can protect a person
up to 30 years. There are a handful of vaccines that
require boosters for continued protection.
Herd immunity saves the world!
When a significantly large proportion of the commu-
nity has protective immunity against a certain vaccine
preventable disease, the bacteria or virus can hardly
find a susceptible person in the community to infect.
The whole community is therefore protected against
the disease, which is known as herd immunity.
The presence of herd immunity conferred by high
vaccination coverage will protect this susceptible
group from getting an infection. Immunisation does
not just protect the individual who has been vac-
cinated but entire families, communities and even
countries as well.
As members of the community, we are given the
responsibility to protect those who are not suitable
to be immunised but are at a high risk of contracting
an infection, such as children who have cancer and
would have to undergo chemotherapy. — The Health
15
Vaccination
is a must!
Under-vaccination and non-vaccination: the sepsis culprit!
By Dr Tan Toh Leong
I
n Malaysia, four deaths due to diphtheria
occurred in 2016 to 2019. In all of these cases,
the children never received any vaccination for
diphtheria. And all of them died from sepsis
due to diphtheria. Ironically, diphtheria had
almost been eliminated from the world because
of vaccination, and the disease was once considered
contained.
Sadly, these four children were not vaccinated, and
their deaths were a tragic and painful experience for
their families once they realized the deaths of their
children could be prevented via vaccination. Death
by sepsis due to smallpox, diphtheria, measles &
poliomyelitis are all preventable via vaccination. The
current situation is truly worrisome.
Herd immunity
What is herd immunity? It is a situation where
majority of the population are immunised and
protected against a disease. When the percentage of
immunised population against a disease is high
(>95%), it will protect those who missed their
vaccination. However, when herd immunisation
effect is less than 95%, those who are not vaccinated
will be at risk of contracting diseases preventable by
vaccination.
Why is good herd immunity important? It is
important in order to eliminate deadly diseases from
the community (e.g. smallpox, diphtheria, measles
& poliomyelitis etc.). The majority or all members
of a population have to be immunised against the
diseases via vaccination for herd immunity to exist
and become strong.
With good coverage of vaccination, over a number
of years, the targeted disease will slowly reduce in
the population. These ancient diseases were almost
successfully eliminated from the world. Good herd
immunity also protects those who are unfit for vacci-
nation (e.g. those who are undergoing chemotherapy,
very young new-born infants, immunity-compro-
mised individuals). However recently, due to low herd
immunity, these diseases have made a comeback!
Why is our herd immunity
becoming weak?
What contributes to low herd immunisation? Three
major factors contribute to this, namely under-
vaccination, non-vaccination and influx of large
unvaccinated population into a vaccinated population
(as in the case of foreign worker’s influx).
Under-vaccination, or miss-vaccination, refers to
individuals who received at least one but not all of the
recommended dose of vaccination. Non-vaccination
means an individual did not receive the recommended
vaccine at all. The third factor i.e. major influx of non-
vaccinated foreigner workers will dilute the initial
herd immunity in a population, and some of them
also carry otherwise extinct infectious diseases into
our country and spread these diseases unintentionally
to the local population.
With good coverage
of vaccination, over
a number of years,
the targeted disease
will slowly reduce
in the population.
These ancient
diseases were
almost successfully
eliminated from
the world. Good
herd immunity
also protects those
who are unfit
for vaccination.
However recently,
due to low herd
immunity, these
diseases have made
a comeback!"
Actions must be taken quickly
Is this situation serious? Does action need to
be taken? Yes! The herd immunity for Malaysia
in general was at 92 percent in 2017 and it is
on the descending trend. Alarmingly, the actual
numbers are maybe lower (less than 90%), as it
is impossible to account for illegal unvaccinated
foreigners who have overstayed in Malaysia.
Furthermore, the anti-vaccination movement
increased the under- and non-vaccinated
population, worsening the situation of low herd
immunity in our population.
Let’s do the math. Let’s say a community
consists of 100 individuals. In order to achieve
a good herd immunity, we need at least 95 indi-
viduals to be vaccinated to achieve 95% herd
immunity. However, when there is an influx
of another 50 non-vaccinated foreign workers
into this community, the herd immunity will
be reduced to 63% (95 vaccinated individuals
over total of 150 individuals in the community).
When we add on the families who refuse to vac-
cinate their children, herd immunity will be even
lower than 63%!
A choice or a responsibility?
Is vaccination a choice or a public responsibility?
There is no direct answer to this. The govern-
ment urges all individuals to be responsible in
protecting members of the community who
are at risk of vaccine-preventable infections.
Stakeholders should have strategised ways to
make sure foreign workers are immunised before
working in our country and prevent them from
overstaying.
Let the responsibility starts from us. Let’s
protect our future generation. Vaccination is a
MUST! — The Health
Dr Tan is currently the President for the Malay-
sian Sepsis Alliance and a member of the Global
Sepsis Alliance. He also holds the position of Senior
Lecturer, Consultant Emergency Physician, and
Student Affair Coordinator (Alumni) at Hospital
Canselor Tuanku Muhriz UKM.