Hong Yang, Ph.D.Hong Yang, Ph.D.Office of Biostatistics and EpidemiologyOffice of Biostatistics and Epidemiology

FDA-Center for Biologics Evaluation & ResearchFDA-Center for Biologics Evaluation & Research

Transmissible Spongiform Encephalopathies Transmissible Spongiform Encephalopathies Advisory Committee Meeting Advisory Committee Meeting

August 1 2011August 1 2011, Gaithersburg MDGaithersburg MD

Potential Effects of Additional Donor Deferrals on the U.S. Blood Supply

Background─ vCJD Risk in Saudi Arabia (SA)

• 3 vCJD cases attributed to residence in SA have been reported

• Information on vCJD risk in SA is limited• vCJD risk likely associated with exposure to bovine

spongiform encephalopathy (BSE) agent during extended residence in SA during years 1980-1996

• Major risk likely from imported beef, feed materials, and live cattle from UK– ~10% beef consumed in SA during 1980-1996 imported from UK– US military base in SA participated UK Beef Program prior to 1990

(possibly significant amount of beef imported from UK)

• Risk associated with imported beef from Europe unknown• Indigenous BSE risk in SA unknown

Background─ FDA’s Assumptions

and Considerations for Donor Deferral

• FDA’s Assumptions– vCJD risk in US military bases in SA similar to risk in

military bases in Europe– vCJD risk in SA similar to risk in countries in western

Europe except the risk in SA ended at 1996

• FDA’s ConsiderationsIndefinitely defer US donors, who – spend >6 months cumulatively in SA as military

personnel during the years 1980-1996 – otherwise spent > 5 years cumulatively in SA during the

year 1980-1996

Four Potential at-risk Groups Affected (1) US Military Personnel deployed to SA, 1980-1996

– UK Beef Program – 1 year deployment– Negligible number of dependents– Most currently donating in civilian blood program

(2) US Military Contractors in SA, 1980-1996– Share same risk as Saudi residents– Time spent ranges from 6 months to 1 year

(3) US Non-Military Contractors in SA, 1980-1996– Time spent ranges from months to >10 years

(4) Saudi Arabian Immigrants who have come to US since 1985– Immigrants prior to 1985 not exposed or stayed <5 years

during years 1980-1996

Population to be Deferred (1):US Military Personnel

• Data: – Number US troops deployed to SA for > 6 months

during years 1980-1996 (NM(1980-1996)): ~ 600,000 (US Department of Defense)

– Percent would be deferred under currently implemented FDA recommendations (Percdf): 30% (US Department of Defense)

• Model Estimate: – Number Military Personnel to be deferred (NDM)

NDM = NM(1980-1996) x (1- Percdf)

Population to be Deferred (2): US Military Contractors

• Data: – Number US Contractors hired by military to work in SA

1980-1996 (NMC(1980-1996)): ~200, 000 (US Department of Defense)

• Assumption:– None have cumulative stay for > 5 years (US

Department of Defense)

• Model Estimate: – Number Military Contractors to be deferred (NDMC)

NDMC = 0

• Data: – 36,000 registered US citizens in SA in 1999 (US State

Department)– Represents annual number US Non-military Contractors

during years 1980-1996 (NNMC-ann)

• AssumptionsAverage Time Spent (Tavg): 4 years

Percent of stay for > 5 years (P>5 yr) : 30%

• Model Estimate: – Number Non-military Contractors to be deferred (NDNMC)

Population to be Deferred (3): US Non-Military Contractors

NDNMC =NNMC-ann x 17 yrs (from 1980 to 1996)

Tavg

x P>5 yr

• Data: – Saudi-born immigrants during years 1989-2010 (US

Department of Homeland Security)

– Average annual number immigrants per year (NI-ann): 920

• Assumption:

All immigrants since 1985 stayed in Saudi Arabia for > 5 years during years 1980-1996

• Model Estimate:

– Number Immigrants to be deferred (NDI)

NDI = NI-ann x 27 yrs (from 1985 to 2011)

Populations to be Deferred (4): Saudi Arabian Immigrants to US

Results: 1Impact of Donor Deferral for Time Spent in SA

on Loss of Blood Donors and Donations

1The results are approximation of loss of donors and donations (confidence intervals of estimates were not obtained)

2Assumption ― 5% donation rate (US Census 2009, HHS 2007)3Assumption ― 1.7 donations per person per year (HHS 2007)

US Military

Personnel

US Military

Contractors

US Non-Military contractors

Saudi Arabian

Immigrants to US

Total

Population to be deferred

420,000 0 45,900 24,800 490,000

2Loss of blood donors

21,000 0 2,300 1,200 24,500

3Loss of blood units

35,700 0 3,900 2,000 41,700

Uncertainties• Limited information for US Non-Military

Contractors – Lack of data on annual number of US Non-Military

Contractors in SA during 1980-1996• Available data for 1999 only• Not all US citizens in SA had registered with US Embassy

– Lack of data on time spent • Varied by employment from months to >10 years

– Sensitivity analysis was conducted to estimate the impact of uncertainties on the estimated loss of donations

• Data on Saudi-born Immigrants do not include immigrants who were non-Saudi nationals– Uncertainty expected to have small impact on estimates of

total loss of donors and donations from all groups

Sensitivity Analysis:Alternative Assumptions on

Annual Number and Time Spent of US Non-Military Contractors

Worst case scenario

Most likely scenario

Best case scenario

Annual number

Non-Military Contractors

45,000 36,000 30,000

Average

time spent (years)

5 4 2

Percent

stay for > 5 years

100% 30% 10%

Results of Sensitivity Analysis ― Impact of Uncertainties on Data of

US Non-Military Contractors on Estimated Donations Lost

Worst case

scenario

Most likely

scenario

Best case

scenario

Loss of blood unitsfrom Non-MilitaryContractors only

13,100 3,900 2,200

Total loss of bloodunits from all riskgroups

50,900 41,700 40,000

Conclusions

• Additional deferral for time spent in SA may results in a total loss of approximately 25,000 donors and 42,000 donations every year from groups of US Military Personnel, US Non-military Contractors and Saudi Arabian Immigrants

• The impact on US blood supply predicted to be small; the loss of donors and donations are approximately 0.2% of current donors and donations

• Uncertainty of the data for Non-Military Contractors predicted to have small impact on estimated loss of blood donations

Acknowledgments

Steven Anderson, OBEDavid M. Asher, OBRRJay Epstein, OBRRLuisa Gregori, OBRRMelissa Greenward, OCTGTPedro Piccardo, OBRRGinette Michaud, OBRRJennifer Scharpf, OBRR

Alternative Policy Option: 6-month Deferral for All Donors

Alternative recommendations:Permanently defer US donors with a history of residence in SA for cumulative stay >6 months during 1980-1996

Populations to be deferred:– 60% US Military Personnel, 1980-1996

• 90% total US military personnel stayed > 6months• 30% military personnel have already been deferred

– All US Military Contractors, 1980-1996– All US Non-Military Contractors, 1980-1996– All Saudi Arabian Immigrants to US since 1980

Results ― Estimate of Loss of Blood Donors and Donations under Alternative

Policy Option

US Military

Personnel

US Military Contractors

US Non-Military

contractors

Saudi Arabian Immigrants

To US

Total

Population to be deferred

420,000 200,000 153,000 29,400 802,400

Number of blood donors lost

21,000 10,000 7,700 1,500 40,200

Number of blood units lost

35,700 17,000 13,000 2,500 68,200