# CDC Yellow Book vs Syphilis Tools

The clearest difference is review sentiment: Syphilis Tools at 100% against CDC Yellow Book's 20%. Syphilis Tools also leads on in-app purchases (none vs 2) and update cadence (every 11 days vs every 17 months). CDC Yellow Book's advantage is ratings volume (69 vs 2). On price, ads, device support and iOS requirement there is nothing between them.

Both are free to download. CDC Yellow Book sells 1 one-off in-app purchase. Syphilis Tools asks for nothing beyond the download.

Syphilis Tools holds the better App Store score, 4.5 against 4.2. That said, the two scores are not equally well evidenced: CDC Yellow Book has 69 ratings behind it against 2, so its average is the more settled of the two. Written reviews point the same way: 20% of CDC Yellow Book's written reviews are positive against 100% of Syphilis Tools's.

CDC Yellow Book ships an update every 17 months, Syphilis Tools every 11 days. The most recent releases landed on October 29, 2026 and October 31, 2026 respectively.

## The numbers

| Metric | CDC Yellow Book | Syphilis Tools |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [4.2 (69 ratings)](https://appshunter.io/ios/app/cdc-yellow-book/id1235766820/reviews) | **[4.5 (2 ratings)](https://appshunter.io/ios/app/syphilis-tools/id6758426004/reviews)** |
| Number of ratings | **69** | 2 |
| Positive reviews | 20.0% of reviews | **100.0% of reviews** |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Every 17 months | **Every 11 days** |
| Monetization | Free with in-app purchases | **Free** |
| Size | 10 MB | 57 MB |
| Requires iOS | 15.0 | 15.0.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 17+ | 17+ |
| Developer | [Unbound Medicine, Inc.](https://appshunter.io/developer/300420400) | [University Of Washington](https://appshunter.io/developer/328228464) |

## What reviewers say

### CDC Yellow Book

[App page](https://appshunter.io/ios/app/cdc-yellow-book/id1235766820)

Access the U.S. government's most current travel health guidelines, including vaccine recommendations and destination-specific advice. This app offers comprehensive information for staying healthy abroad, with features like search, notes, and favorites.

**Highlights:** Pre-travel vaccinations and preventative care, Destination-specific guidelines, Advice for travelers with specific health needs, Full text search, Custom notes and highlights, Reference maps, tables, and charts

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| CDC Yellow Book | $29.99 | one-time |


### Syphilis Tools

[App page](https://appshunter.io/ios/app/syphilis-tools/id6758426004)

This medical reference app provides healthcare professionals and trainees with up-to-date information on diagnosing, treating, and preventing syphilis. It includes tools for screening, serologic testing, staging, treatment, monitoring, and partner management, all based on CDC guidelines.

**Highlights:** CDC STI Treatment Guidelines, Offline accessibility, Geographic Risk Tool, Serologic Testing Interpretation, Nontreponemal Titer Tool, Treatment Regimen Summaries, Partner Management Guidance

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is CDC Yellow Book free?

CDC Yellow Book is free to download, with in-app purchases available.

### Is Syphilis Tools free?

Syphilis Tools is free to download, with no in-app purchases.

### Which has better reviews, CDC Yellow Book or Syphilis Tools?

Syphilis Tools is rated higher. CDC Yellow Book averages 4.2 out of 5 from 69 ratings, while Syphilis Tools averages 4.5 from 2 ratings.

### Do CDC Yellow Book or Syphilis Tools have ads?

Neither CDC Yellow Book nor Syphilis Tools shows ads.

### Which is updated more often, CDC Yellow Book or Syphilis Tools?

CDC Yellow Book ships an update every 17 months, and Syphilis Tools every 11 days. Most recently, CDC Yellow Book was updated on October 29, 2026 and Syphilis Tools on October 31, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*