- COVID-19 booster shots are recommended for various groups when vaccine-induced immunity has waned, typically 3-6 months after the primary vaccination series. Effectiveness against infection declines more rapidly than against severe outcomes like hospitalization and death. - Studies show a third dose of mRNA vaccines like Pfizer significantly increases antibody levels in transplant recipients and the immunocompromised whose immune response is weaker. - Countries providing data found waning vaccine protection against infection over time but sustained effectiveness against severe disease, supporting the need for boosters in vulnerable populations.

1. COVID-19 Vaccine Booster
– when and why?
8 Dec 2021
Kalaiarasu M Peariasamy
Institute for Clinical Research
Ministry of Health Malaysia

2. Malaysia COVID-19 : 2.66m cases & 30.6k death

3. 3
1,356,076 individuals aged 18
years or older with confirmed
SARS-CoV-2 infections from 1
April 2021 to 15 September 2021
BNT162b2, AZD1222, and CoronaVac

4. RecoVaM (1 April to 15 September 2021): All vaccines are effective
*Data covers 1 April 2021 to 15 September 2021, and extracted as at 4 October 2021
Source: RECoVaM
Being fully vaccinated reduces risk of
infection by 88% relative to the unvaccinated
All vaccines reduce the risk of ICU admission substantially
Risk of symptomatic infection falls by 85%
when vaccinated
All vaccines, including Sinovac, are highly effective at preventing death
87.8
0
20
40
60
80
100
National Average
VE Against Infection: Screening Method
%
85.4
0
20
40
60
80
100
National Average
VE Against Symptomatic Infection: Screening Method
%
95.6
90.3
72.0
0
20
40
60
80
100
AstraZeneca Pfizer Sinovac
VE Against ICU Admission: Logistic Regression
%
95.3 92.7
82.4
0
20
40
60
80
100
AstraZeneca Pfizer Sinovac
VE Against Death: Logistic Regression
%

5. Malaysia Situation Report

6. HCW Serosurveillance
• April 2020 - May 2020
• 400 Healthcare Workers
• Quota sampling
• National Public Health Laboratory
• 2 COVID-19 designated hospitals
• Result
• Zero seroprevalence among HCW
• Very high adherence to PPE

7. Serosurveillance Study - cohort of
Malaysia healthcare workers (HCW)
551 Healthcare workers
• Before 1st & 2nd dose of BNT162b2 vaccine
• 2 weeks after 2nd dose
• Follow-up at 3, 6, 12, 18, 24 months
Serology Sampling
• 5mls of blood samples
• Separate serum >> store at -80 ⁰C freezer
>> thaw samples >> run serology test
Ethics approval: NMRR-21-65-58212

8. Assessment of Exposure Risk
Symptoms reporting
• SMS reminder every 2 weeks
• Case definitions as per MOH guidelines
• https://covid-19.moh.gov.my/garis-panduan/garis-panduan-
kkm/ANNEX_21_Mgmt_of_Healthcare_Workers_HCW_During_COVID-19_Pandemic_30102021.pdf
COVID-19 RT-PCR test
• If symptoms fulfil clinical criteria
• Close contact
• Hospital OSH routine swab at workplace

9. Summary of Findings
• Following BNT162b2 vaccination, IgG titre peaks at 2 weeks and wanes in
3 – 6 months
• During the 3 – 6 months period, we observed a spike in breakthrough
cases coinciding with increase in community cases and delta wave
• Breakthrough infections
• Individuals with asymptomatic infection do not develop high antibody response
• Individuals with mild symptoms develop higher antibody response

10. SPIKE-ANTIBODY WANING AFTER
SECOND DOSE OF BNT162b2 or ChAdOx1
10
• n=605, 14-15 Jun 2021 samples collected
• 321 (53%) women
• median age was 63 years (IQR 58–67).
• 186 (31%) were categorised as clinically vulnerable
• 117 (19%) as clinically extremely vulnerable
• 302 (50%) as not clinically vulnerable.
• Higher antibody levels in vulnerable groups for
BNT162b2 and the reverse for ChAdOx1
• Trend for declining S-antibody levels with time remains
consistent, and the low levels in clinically vulnerable
ChAdOx1 vaccinees at 70 days
https://doi.org/10.1016/ S0140-6736(21)01642-1

11. RECoVaM - Clear waning of effectiveness
against infections
Note 1: VE against infection is estimated using a negative binomial regression on a retrospective cohort of the population, and VE against severe outcomes are estimated with a logistic regression on a retrospective cohort of
confirmed COVID-19 cases; all COVID-19 cases are restricted to September 2021
Note 2: Estimates as at 18 November 2021 (Severe Outcomes), based on data up to 30 September 2021; figures may change subject to data revisions
Source: RECoVaM
88.7
68.0
0
20
40
60
80
100
1-2 Months 3-5 Months
Pfizer: VE Against Infection
%
76.1
27.9
0
20
40
60
80
100
1-2 Months 3-5 Months
Sinovac: VE Against Infection
%

12. Evidence from other countries suggest clear waning of effectiveness against infection,
but limited waning of effectiveness against severe outcomes
Source: Chemaitelly et al (2021), Tartof et al (2021), Andrews et al (2021)
Country Findings
Qatar Pfizer
• Infection: Fell from 78% to 20% (after 4 months)
• Severe, Critical and Fatal: Remained at 96% (after 6 months)
US Pfizer
• Infection: Down from 88% to 47% (after 5 months)
• Hospitalisation: Remained at 93% (after 6 months)
UK
Pfizer
• Symptomatic: 92% to 70% (after 4.5 months)
• Hospitalisation: 99% to 93% (after 4.5 months)
• Death: 98% to 90% (after 4.5 months)
AstraZeneca
• Symptomatic: 67% to 47% (after 4.5 months)
• Hospitalisation: 95% to 77% (after 4.5 months)
• Death: 94% to 78% (after 4.5 months)

13. 13
In this case-control study, being unvaccinated was associated with 2.34 times the odds of reinfection
compared with being fully vaccinated
https://www.cdc.gov/mmwr/volumes/70/wr/pdfs/mm7032e1-H.pdf

14. 14
BOOSTER DOSE : 3rd DOSE COMIRNATY IN
SOLID ORGAN TRANSPLANT RECIPIENTS

16. • Individuals who had experienced
SARS-CoV-2 infection prior to
vaccination showed large nAb
increase on second antigen
exposure (i.e., after first vaccine
dose)
• In contrast, nAb responses against
Wuhan Hu-1 and VOCs B.1.351, P.1
and B.1.617.2 plateaued or
decreased between the second and
third antigen exposure.

17. • Trial demonstrated the potential of all 7 vaccines tested to boost immunity after primary vaccination with
ChAd/ChAd and of six vaccines after an initial course of BNT/BNT.
• Side effect data show all seven vaccines are safe to use as 3rd doses
• Acceptable levels of inflammatory side effects like injection site pain, muscle soreness, fatigue.

18. COVID-19 Vaccine Effectiveness (VE)
Assessment in Chile
• Ministry of Health, Chile, 17 Oct 2021
• Protection against COVID19
Booster
Vaccine
VE 2 weeks
after Primary
Series of
Sinovac
VE 2 weeks
after Booster
Vaccine
VE Differences
Compared to
Pfizer
Pfizer
54%
95% -
AstraZeneca 94% 1% less
Sinovac 74% 21% less

19. COVID-19 Vaccine Effectiveness (VE)
Assessment in Chile
• Ministry of Health, Chile, 17 Oct 2021
• Protection against Hospital Admission
Booster
Vaccine
VE 2 weeks
after Primary
Series of
Sinovac
VE 2 weeks
after Booster
Vaccine
VE Differences
Compared to
Pfizer
Pfizer
83%
91% -
AstraZeneca 97% 6% more
Sinovac 81% 10% less

20. COVID-19 Vaccine Effectiveness (VE)
Assessment in Chile
• Ministry of Health, Chile, 17 Oct 2021
• Protection against ICU Admission
Booster
Vaccine
VE 2 weeks
after Primary
Series of
Sinovac
VE 2 weeks
after Booster
Vaccine
VE Differences
Compared to
Pfizer
Pfizer
87%
92% -
AstraZeneca 99% 7% more
Sinovac 85% 7% less

22. • JCVI advises that all adults aged 40 to 49 should also be offered
a booster vaccination with an mRNA COVID-19 vaccine, 6 months
after their second dose, irrespective of the vaccines given for the
first and second doses.
• Future considerations include the need for booster vaccination
(third dose) for 18 to 39 year olds who are not in an at-risk group
• JCVI updated that
adults aged 18 years
and above are eligible
for a booster vaccine.
• The booster vaccine
dose should be given
no sooner than 3
months after the
primary course.
Published 15 November 2021

23. Target population for Booster
Recommended Population
• Frontline Healthcare worker
• Elderly ≥60 years
• Long term care facilities individuals (staff and residents)
• Individuals aged ≥18 years with underlying medical conditions
Additional Recommended Population
• Pregnant mothers
• Essential frontline workers
• For travel restrictions, pilgrimage
• All adults aged 18 years and above

24. Booster Vaccine Recommendation
Vaccine
Manufacturer
When to Give Booster Recommended Vaccine Alternatives
Pfizer BioNTech 6 months after 2nd dose Pfizer (Corminarty) AstraZeneca (Vaxzevria)
AstraZeneca 6 months after 2nd dose Pfizer (Corminarty)
AstraZeneca (Vaxzevria)
-
Sinovac Biotech 3 months after 2nd dose Pfizer (Corminarty)
Sinovac (CoronaVac)
AstraZeneca (Vaxzevria)
Sinopharm 3 months after 2nd dose Pfizer (Corminarty)
Sinopharm – Covilo (Pending product owner submission)
AstraZeneca (Vaxzevria)
Moderna 6 months after 2nd dose Pfizer (Corminarty)
Half dose Moderna - Spikevax (Pending product owner
submission)
Janssen (Pending product owner submission)
AstraZeneca (Vaxzevria)
CanSino Biologics 6 months after 1st dose
Pfizer (Corminarty)
Cansino Bio – Convidecia (Pending NPRA review)
AstraZeneca (Vaxzevria)
Janssen 2 months after 1st dose Pfizer (Corminarty)
Janssen (Pending product owner submission)
Half dose Moderna - Spikevax (Pending product owner
submission)
AstraZeneca (Vaxzevria)
*AstraZeneca Vaccine – Recommended for aged 50 years and above for those who are first time receiving Vaxzevria. Adults aged 18 years
and above can make their decision based on risk benefit assessment.

25. 3rd Dose Vaccine Recommendation
Vaccine Manufacturer When to 3rd Dose Recommended Vaccine Comments
Pfizer BioNTech At least 4 weeks after 2nd dose
Pfizer (Corminarty)
Moderately or severely
immunocompromised individuals
AstraZeneca At least 8 weeks after 2nd dose AstraZeneca (Vaxzevria)
Pfizer (Corminarty)
Moderately or severely
immunocompromised individuals
Sinovac At least 4 weeks after 2nd dose
At least 90 days after 2nd dose
Pfizer (Corminarty)
Sinovac (CoronaVac)
Immunocompromised individuals
All adults