This letter appeared in AIDS in July 2001 (Vol. 15, No. 10, pages 1321-1322).

 

Increasing incidence of HIV infections among young gay and bisexual men in Vancouver

 
Robert S. Hogg, Amy E. Weber, Keith Chan, Steve Martindale, Darrel Cook*, Mary Lou Miller, Kevin JP Craib

BC Centre for Excellence in HIV/AIDS; and
(*) the BC Centre for Disease Control, Vancouver, BC.

[View or download the PDF file of this letter.]

 

Since the beginning of the HIV epidemic in North America, the majority of HIV infections have occurred among men who engage in sexual relations with other men. As the HIV epidemic enters its third decade, gay and bisexual men continue to have among the highest rates of HIV infection. Previous studies have highlighted the decline in HIV incidence and risk behaviour among gay and bisexual men [1,2]. However, several studies have suggested that young gay and bisexual men continue to engage in unprotected sexual behaviours and are at continued risk of HIV infection [3,4]. Recent reports in the media [5­9] and research literature [10, 11] have indicated an increase in the incidence of HIV among gay and bisexual in many of the world's major cities. The purpose of this study was to determine trends in HIV incidence using data from a prospective cohort of young gay and bisexual men.

The Vanguard Project is a prospective study of gay and bisexual men aged 15 to 30, living in the Greater Vancouver region. These men were recruited through outreach, clinics, and physicians' offices. To be eligible for this longitudinal study the participants must have not previously tested positive for HIV and must have self-identified as gay or bisexual or have had sex with other men. Vanguard participants have completed a self-administered questionnaire and undergone HIV antibody testing on an annual basis since May 1995.

HIV incidence was calculated per annum as the number of new infections divided by the total person-time under observation for each calendar year from study inception through December 2000. Person-time was calculated as the interval between enrolment and the most recent follow-up visit for subjects who did not seroconvert. For subjects who became HIV positive, person-time was calculated as the interval between enrolment and the first visit at which an HIV positive test result was detected. Ninety-five percent confidence intervals for the incidence estimates were calculated based on the Poisson distribution.

As of December 31, 2000, 668 men had completed at least one questionnaire and two HIV tests. Table 1 provides a summary of HIV incidence in the cohort by year since its inception in 1995. As shown here 25 HIV infections were prospectively observed over the follow-up period (mean follow-up: 2.87 years), resulting in an overall incidence rate of 1.3 per 100 person-years (95% Confidence Interval (CI): 0.8-1.8). Among participants who reported injection drug use the incidence rate was higher (3.9/100 person-years) than among those participants who did not report the use of injection drugs (0.9/100 person-years). A significant increase in new HIV infections was observed between 1995-1999 and 2000 within the entire cohort; this remained true when participants who had injected drugs were excluded from the analysis (p<0.05). Among men who have never injected drugs, the rate of new infections has increased from 0.6 per 100 person years in 1995-99 (95%CI: 0.2-1.0) to 3.2 per 100 person years in the year 2000 (95%CI: 0.6-5.8).

The observed increase in incidence in our cohort corroborates previous reports from other major cities [6­12]. Further, the upturn in HIV incidence is consistent with increased rates of rectal gonorrhea and sexual risk behaviour reported among gay and bisexual men [13]. Overall, these studies suggest the need for continued vigilant surveillance and further investigation of the determinants of seroconversion in order to assist with the efforts to stabilize or decrease seroincidence in this population of men.

Table 1:
Incidence of HIV infection among gay and bisexual men enrolled in the Vanguard Project, by calendar year and category

All participants
(n = 668)

Non-IDUs
(n= 590)

Injection drug users
(n = 76)

Year

New infections

Rate
(95% CI)

New infections

Rate
(95% CI)

New infections

Rate
(95% CI)

1995

1

1.9%
(0.0-5.7)

1

2.1%
(0.0-6.1)

0

n/a

1996

4

1.3%
(0.0-2.6)

3

1.1%
(0.0-2.3)

1

4.1%
(0.0-12.1)

1997

4

0.9%
(0.0-1.8)

1

0.2%
(0.0-0.7)

3

9.4%
(0.0-20.1)

1998

5

1.1%
(0.1-2.0)

4

0.9%
(0.0-1.9)

0

n/a

1999

1

0.2%
(0.0-0.7)

1

0.3%
(0.0-0.8)

0

n/a

2000

11*

5.0%
(2.1-8.0)

7

3.7%
(1.0-6.5)

3

9.6%
(0.0-20.6)
             

1995-99

15*

0.9%
(0.4-1.3)

10

0.6%
(0.2-1.0)

4

2.7%
(0.1-5.3)

All years

26*

1.4%
(0.8-1.9)

17

1.0%
(0.5-1.4)

7

3.9%
(1.0-6.8)
CI: Confidence Interval.
* Data regarding injection drug use were unavailable for two seroconverters.

 

LITERATURE CITED

1. Kingsley LA, Zhou SYJ, Bacellar H, Rinaldo CRJ, Chmiel J, Detels R, et al. Temporal trends in human immunodeficiency virus type 1 seroconversion 1984-1989: a report from the Multicenter AIDS Cohort Study (MACS). American Journal of Epidemiology 1991,134:331-9.
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2. van Griensven GJP, De Vroome EMM, Goudsmit J, Coutinho RA. Changes in sexual behaviour and the fall in incidence of HIV infection among homosexual men. BMJ 1989,298:218-21.

3. Hays RB, Kegeles SM, Coates TJ. High HIV risk-taking among young gay men. AIDS 1990,4:901-7.
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4. Strathdee SA, Hogg RS, Martindale SL, Cornelisse PGA, Craib KJP, Montaner JSG, et al. Determinants of sexual risk-taking among young HIV-negative gay and bisexual men. Journal of Acquired Immune Deficiency Syndroms and Human Retrovirology 1998,19:61-6.

5. Quinn A. HIV cases double in gay capital. The Gazette 2000 July 3,2000.
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6. Russell S. S.F. HIV rate surges: Alarming incidence of new infections raises fears of scourge to come. San Francisco Chronicle 2000 June 30, 2000.
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7. Quinn J. HIV rate rising among gay men. Tronto Star 2000 July 4, 2000.

8. Song J. Studies see increasing risk by gay men: Three local surveys prove particularly alarming to scientists who fear a resurgence of AIDS. Los Angeles Times 2001 February 17, 2001.

9. Torassa. San Francisco's HIV infection rate doubles. San Franscisco Chronicle 2001 January 24, 2001.

10. Dodds JP, Nardone A, Mercey DE, Johnson AM. Increase in high risk sexual behaviour among homosexual men, London 1996-8: cross sectional, questionnaire study. BMJ 2000,320:1510-1.
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11. Kellogg T, McFarland W, Katz M. Recent increases in HIV serconversions among repeat anonymous testers in San Francisco. AIDS 1999,13:2303-4.

12. Brown D. High HIV rates seen in young Studies also note 'prevention fatigue' in older infected people. Washington Post 2001 February 7, 2001.

13. Centers for Disease Control and Prevention. Increases in unsafe sex and rectal gonorrhea among men who have sex with men - San Francisco, California, 1994-1997. MMWR 1999,48:45-8.
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For more information, contact:

Bonnie Devlin
Vanguard Project Coordinator
608 - 1081 Burrard Street
Vancouver, BC, Canada, V6Z 1Y6
Tel: (604)806-8306
Fax: (604)806-9044